Body parameters

• messages: array of MessageParam

  Input messages.

  Our models are trained to operate on alternating user and assistant conversational turns. When creating a new Message, you specify the prior conversational turns with the messages parameter, and the model then generates the next Message in the conversation. Consecutive user or assistant turns in your request will be combined into a single turn.

  Each input message must be an object with a role and content. You can specify a single user-role message, or you can include multiple user and assistant messages.

  If the final message uses the assistant role, the response content will continue immediately from the content in that message. This can be used to constrain part of the model's response.

  Example with a single user message:

  [{"role": "user", "content": "Hello, Claude"}]

  Example with multiple conversational turns:

  [
    {"role": "user", "content": "Hello there."},
    {"role": "assistant", "content": "Hi, I'm Claude. How can I help you?"},
    {"role": "user", "content": "Can you explain LLMs in plain English?"},
  ]

  Example with a partially-filled response from Claude:

  [
    {"role": "user", "content": "What's the Greek name for Sun? (A) Sol (B) Helios (C) Sun"},
    {"role": "assistant", "content": "The best answer is ("},
  ]

  Each input message content may be either a single string or an array of content blocks, where each block has a specific type. Using a string for content is shorthand for an array of one content block of type "text". The following input messages are equivalent:

  {"role": "user", "content": "Hello, Claude"}

  {"role": "user", "content": [{"type": "text", "text": "Hello, Claude"}]}

  See input examples.

  Note that if you want to include a system prompt, you can use the top-level system parameter — there is no "system" role for input messages in the Messages API.

  There is a limit of 100,000 messages in a single request.

  • content: string or array of ContentBlockParam

    • string

    • array of ContentBlockParam

      • TextBlockParam object

        • type: "text"

        • text: string

          minLength: 1

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

          • type: "ephemeral"

          • ttl: optional "5m" or "1h"

            The time-to-live for the cache control breakpoint.

            This may be one the following values:

            • 5m: 5 minutes
            • 1h: 1 hour

            Defaults to 5m. See prompt caching pricing for details.

            • "5m"

            • "1h"

        • citations: optional array of TextCitationParam or null

          • CitationCharLocationParam object

            • type: "char_location"

            • cited_text: string

            • document_index: number

              minimum: 0

            • document_title: string or null

              maxLength: 500, minLength: 1

            • end_char_index: number

            • start_char_index: number

              minimum: 0

          • CitationPageLocationParam object

            • type: "page_location"

            • cited_text: string

            • document_index: number

              minimum: 0

            • document_title: string or null

              maxLength: 500, minLength: 1

            • end_page_number: number

            • start_page_number: number

              minimum: 1

          • CitationContentBlockLocationParam object

            • type: "content_block_location"

            • cited_text: string

              The full text of the cited block range, concatenated.

              Always equals the contents of content[start_block_index:end_block_index] joined together. The text block is the minimal citable unit; this field is never a substring of a single block. Not counted toward output tokens, and not counted toward input tokens when sent back in subsequent turns.

            • document_index: number

              minimum: 0

            • document_title: string or null

              maxLength: 500, minLength: 1

            • end_block_index: number

              Exclusive 0-based end index of the cited block range in the source's content array.

              Always greater than start_block_index; a single-block citation has end_block_index = start_block_index + 1.

            • start_block_index: number

              0-based index of the first cited block in the source's content array.

              minimum: 0

          • CitationWebSearchResultLocationParam object

            • type: "web_search_result_location"

            • cited_text: string

            • encrypted_index: string

            • title: string or null

              maxLength: 512, minLength: 1

            • url: string

              minLength: 1

          • CitationSearchResultLocationParam object

            • type: "search_result_location"

            • cited_text: string

              The full text of the cited block range, concatenated.

              Always equals the contents of content[start_block_index:end_block_index] joined together. The text block is the minimal citable unit; this field is never a substring of a single block. Not counted toward output tokens, and not counted toward input tokens when sent back in subsequent turns.

            • end_block_index: number

              Exclusive 0-based end index of the cited block range in the source's content array.

              Always greater than start_block_index; a single-block citation has end_block_index = start_block_index + 1.

            • search_result_index: number

              0-based index of the cited search result among all search_result content blocks in the request, in the order they appear across messages and tool results.

              Counted separately from document_index; server-side web search results are not included in this count.

              minimum: 0

            • source: string

            • start_block_index: number

              0-based index of the first cited block in the source's content array.

              minimum: 0

            • title: string or null

      • ImageBlockParam object

        • type: "image"

        • source: Base64ImageSource or URLImageSource or FileImageSource

          • Base64ImageSource object

            • type: "base64"

            • data: string

              format: byte

            • media_type: "image/jpeg" or "image/png" or "image/gif" or "image/webp"

              • "image/jpeg"

              • "image/png"

              • "image/gif"

              • "image/webp"

          • URLImageSource object

            • type: "url"

            • url: string

          • FileImageSource object

            • type: "file"

            • file_id: string

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • transformations: optional ImageTransformationsParam or null

          Configures the transformations the server applies to this image before the model observes it. Each key names a condition the server transforms images for; its value selects the transformation applied. Omitted keys keep their default behavior, and an empty object is equivalent to omitting the field.

          • oversized_image: optional "downsize" or "error"

            What the server does when this image exceeds the model's maximum image size. "downsize" (the default) scales the image down to fit, which changes the dimensions the model observes without telling you. "error" instead rejects the request with a 400 error naming the image's dimensions and the largest dimensions that fit, so you can scale the image deliberately — your image is never silently scaled down.

            • "downsize"

            • "error"

      • DocumentBlockParam object

        • type: "document"

        • source: Base64PDFSource or PlainTextSource or ContentBlockSource or 2 more

          • Base64PDFSource object

            • type: "base64"

            • data: string

              format: byte

            • media_type: "application/pdf"

          • PlainTextSource object

            • type: "text"

            • data: string

            • media_type: "text/plain"

          • ContentBlockSource object

            • type: "content"

            • content: string or array of ContentBlockSourceContent

              • string

              • ContentBlockSourceContent = array of ContentBlockSourceContent

                • TextBlockParam object

                • ImageBlockParam object

          • URLPDFSource object

            • type: "url"

            • url: string

          • FileDocumentSource object

            • type: "file"

            • file_id: string

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • citations: optional CitationsConfigParam or null

          • enabled: optional boolean

        • context: optional string or null

          minLength: 1

        • title: optional string or null

          maxLength: 500, minLength: 1

      • SearchResultBlockParam object

        • type: "search_result"

        • content: array of TextBlockParam

          • type: "text"

          • text: string

            minLength: 1

          • cache_control: optional CacheControlEphemeral or null

            Create a cache control breakpoint at this content block.

          • citations: optional array of TextCitationParam or null

        • source: string

        • title: string

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • citations: optional CitationsConfigParam

      • ThinkingBlockParam object

        • type: "thinking"

        • signature: string

          The signature value of this thinking block, exactly as returned by the API in a previous response. Used to verify that the block was generated by Claude.

          Thinking blocks must be passed back unmodified and in their original order; a modified block results in a 400 invalid_request_error.

        • thinking: string

          The thinking text of this block as returned by the API.

      • RedactedThinkingBlockParam object

        • type: "redacted_thinking"

        • data: string

          The data value of this redacted thinking block, exactly as returned by the API in a previous response. Opaque and encrypted; pass it back unchanged.

      • ToolUseBlockParam object

        • type: "tool_use"

        • id: string

          pattern: ^[a-zA-Z0-9_-]+$

        • input: map[unknown]

        • name: string

          maxLength: 200, minLength: 1

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • caller: optional DirectCaller or ServerToolCaller or ServerToolCaller20260120

          Tool invocation directly from the model.

          • DirectCaller object

            Tool invocation directly from the model.

            • type: "direct"

          • ServerToolCaller object

            Tool invocation generated by a server-side tool.

            • type: "code_execution_20250825"

            • tool_id: string

              pattern: ^srvtoolu_[a-zA-Z0-9_]+$

          • ServerToolCaller20260120 object

            • type: "code_execution_20260120"

            • tool_id: string

              pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • toolset_name: optional string or null

          For a toolset member tool_use, the toolset family this member belongs to.

          maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$

      • ToolResultBlockParam object

        • type: "tool_result"

        • tool_use_id: string

          pattern: ^[a-zA-Z0-9_-]+$

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • content: optional string or array of TextBlockParam or ImageBlockParam or SearchResultBlockParam or 3 more

          • string

          • array of TextBlockParam or ImageBlockParam or SearchResultBlockParam or 3 more

            • TextBlockParam object

            • ImageBlockParam object

            • SearchResultBlockParam object

            • DocumentBlockParam object

            • ToolReferenceBlockParam object

              Tool reference block that can be included in tool_result content.

              • type: "tool_reference"

              • tool_name: string

                maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$

              • cache_control: optional CacheControlEphemeral or null

                Create a cache control breakpoint at this content block.

            • BrowserStateBlockParam object

              The caller's browser state after a browser toolset member call — the full inventory of open tabs, which tab is active, and any side effects (tabs opened, download state changes) the call produced.

              At most one per tool_result, only on a non-error result answering a browser toolset member tool_use. The server renders the model-visible text from it; the model never sees the raw fields.

              • type: "browser_state"

              • tabs: array of BrowserStateTabEntry

                All tabs open in the browser after this call — the full inventory, not a delta. May be empty. Whenever non-empty, exactly one entry carries active: true.

                maxItems: 100

                • tab_id: string

                  The caller-assigned identifier for this tab, unique within the inventory.

                  maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                • title: string

                  The title of the page the tab is showing. May be empty.

                  maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                • url: string

                  The URL of the page the tab is showing. May be empty.

                  maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                • active: optional boolean

                  Whether this tab is the active tab after this call. Whenever tabs is non-empty, exactly one entry is marked active: true.

              • cache_control: optional CacheControlEphemeral or null

                Create a cache control breakpoint at this content block.

              • state_changes: optional array of BrowserStateChange or null

                Tabs opened and download state changes during this call. "Nothing to report" is expressed by omitting the field, never by an empty list.

                maxItems: 200, minItems: 1

                • BrowserStateChangeTabOpened object

                  A tab this call's execution opened that remains open at its end — the creation delta of the tabs inventory, not an event log.

                  Carries only the tab_id; the tab's title and url live on its tabs entry, which must include the same tab_id. A tab opened during a failed call gets no deferred tab_opened; it simply appears in the next result's tabs inventory.

                  • type: "tab_opened"

                  • tab_id: string

                    The tab_id of the opened tab, present in tabs.

                    maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                • BrowserStateChangeDownloadStarted object

                  A file download that started during this call.

                  • type: "download_started"

                  • download_id: string

                    The caller-assigned identifier for this download, stable across the state changes reporting it.

                    maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                  • url: string

                    The final post-redirect URL the download was served from.

                    maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                • BrowserStateChangeDownloadCompleted object

                  A file download that finished during this call, reported with the same download_id as its download_started — or without a prior download_started, when the download finished during the call that started it (at most one state change per download_id per result).

                  • type: "download_completed"

                  • download_id: string

                    The caller-assigned identifier for this download, stable across the state changes reporting it.

                    maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                  • url: string

                    The final post-redirect URL the download was served from.

                    maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                  • path: optional string or null

                    Where the executor saved the file, on the executor's filesystem. Only included when another tool in the same environment can read the file at that path.

                    pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096

                  • size_bytes: optional number or null

                    The completed download's size.

                    minimum: 0

                • BrowserStateChangeDownloadFailed object

                  A file download that failed — or was cancelled — during this call.

                  • type: "download_failed"

                  • download_id: string

                    The caller-assigned identifier for this download, stable across the state changes reporting it.

                    maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                  • url: string

                    The final post-redirect URL the download was served from.

                    maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$

                  • error: optional string or null

                    The failure or cancellation detail, when known.

                    pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096

        • is_error: optional boolean

        • toolset_name: optional string or null

          For a toolset member tool_result, the toolset family of the paired tool_use.

          maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$

      • ServerToolUseBlockParam object

        • type: "server_tool_use"

        • id: string

          pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • input: map[unknown]

        • name: "web_search" or "web_fetch" or "code_execution" or 4 more

          • "web_search"

          • "web_fetch"

          • "code_execution"

          • "bash_code_execution"

          • "text_editor_code_execution"

          • "tool_search_tool_regex"

          • "tool_search_tool_bm25"

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • caller: optional DirectCaller or ServerToolCaller or ServerToolCaller20260120

          Tool invocation directly from the model.

          • DirectCaller object

            Tool invocation directly from the model.

          • ServerToolCaller object

            Tool invocation generated by a server-side tool.

          • ServerToolCaller20260120 object

      • WebSearchToolResultBlockParam object

        • type: "web_search_tool_result"

        • content: WebSearchToolResultBlockParamContent

          • WebSearchToolResultBlockItem = array of WebSearchResultBlockParam

            • type: "web_search_result"

            • encrypted_content: string

            • title: string

            • url: string

            • page_age: optional string or null

          • WebSearchToolRequestError object

            • type: "web_search_tool_result_error"

            • error_code: WebSearchToolResultErrorCode

              • "invalid_tool_input"

              • "unavailable"

              • "max_uses_exceeded"

              • "too_many_requests"

              • "query_too_long"

              • "request_too_large"

        • tool_use_id: string

          pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • caller: optional DirectCaller or ServerToolCaller or ServerToolCaller20260120

          Tool invocation directly from the model.

          • DirectCaller object

            Tool invocation directly from the model.

          • ServerToolCaller object

            Tool invocation generated by a server-side tool.

          • ServerToolCaller20260120 object

      • WebFetchToolResultBlockParam object

        • type: "web_fetch_tool_result"

        • content: WebFetchToolResultErrorBlockParam or WebFetchBlockParam

          • WebFetchToolResultErrorBlockParam object

            • type: "web_fetch_tool_result_error"

            • error_code: WebFetchToolResultErrorCode

              • "invalid_tool_input"

              • "url_too_long"

              • "url_not_allowed"

              • "url_not_in_prior_context"

              • "url_not_accessible"

              • "unsupported_content_type"

              • "too_many_requests"

              • "max_uses_exceeded"

              • "unavailable"

              • "content_too_large"

          • WebFetchBlockParam object

            • type: "web_fetch_result"

            • content: DocumentBlockParam

            • url: string

              Fetched content URL

            • retrieved_at: optional string or null

              ISO 8601 timestamp when the content was retrieved

        • tool_use_id: string

          pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

        • caller: optional DirectCaller or ServerToolCaller or ServerToolCaller20260120

          Tool invocation directly from the model.

          • DirectCaller object

            Tool invocation directly from the model.

          • ServerToolCaller object

            Tool invocation generated by a server-side tool.

          • ServerToolCaller20260120 object

      • CodeExecutionToolResultBlockParam object

        • type: "code_execution_tool_result"

        • content: CodeExecutionToolResultBlockParamContent

          Code execution result with encrypted stdout for PFC + web_search results.

          • CodeExecutionToolResultErrorParam object

            • type: "code_execution_tool_result_error"

            • error_code: CodeExecutionToolResultErrorCode

              • "invalid_tool_input"

              • "unavailable"

              • "too_many_requests"

              • "execution_time_exceeded"

          • CodeExecutionResultBlockParam object

            • type: "code_execution_result"

            • content: array of CodeExecutionOutputBlockParam

              • type: "code_execution_output"

              • file_id: string

            • return_code: number

            • stderr: string

            • stdout: string

          • EncryptedCodeExecutionResultBlockParam object

            Code execution result with encrypted stdout for PFC + web_search results.

            • type: "encrypted_code_execution_result"

            • content: array of CodeExecutionOutputBlockParam

              • type: "code_execution_output"

              • file_id: string

            • encrypted_stdout: string

            • return_code: number

            • stderr: string

        • tool_use_id: string

          pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

      • BashCodeExecutionToolResultBlockParam object

        • type: "bash_code_execution_tool_result"

        • content: BashCodeExecutionToolResultErrorParam or BashCodeExecutionResultBlockParam

          • BashCodeExecutionToolResultErrorParam object

            • type: "bash_code_execution_tool_result_error"

            • error_code: BashCodeExecutionToolResultErrorCode

              • "invalid_tool_input"

              • "unavailable"

              • "too_many_requests"

              • "execution_time_exceeded"

              • "output_file_too_large"

          • BashCodeExecutionResultBlockParam object

            • type: "bash_code_execution_result"

            • content: array of BashCodeExecutionOutputBlockParam

              • type: "bash_code_execution_output"

              • file_id: string

            • return_code: number

            • stderr: string

            • stdout: string

        • tool_use_id: string

          pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

      • TextEditorCodeExecutionToolResultBlockParam object

        • type: "text_editor_code_execution_tool_result"

        • content: TextEditorCodeExecutionToolResultErrorParam or TextEditorCodeExecutionViewResultBlockParam or TextEditorCodeExecutionCreateResultBlockParam or TextEditorCodeExecutionStrReplaceResultBlockParam

          • TextEditorCodeExecutionToolResultErrorParam object

            • type: "text_editor_code_execution_tool_result_error"

            • error_code: TextEditorCodeExecutionToolResultErrorCode

              • "invalid_tool_input"

              • "unavailable"

              • "too_many_requests"

              • "execution_time_exceeded"

              • "file_not_found"

            • error_message: optional string or null

          • TextEditorCodeExecutionViewResultBlockParam object

            • type: "text_editor_code_execution_view_result"

            • content: string

            • file_type: "text" or "image" or "pdf"

              • "text"

              • "image"

              • "pdf"

            • num_lines: optional number or null

            • start_line: optional number or null

            • total_lines: optional number or null

          • TextEditorCodeExecutionCreateResultBlockParam object

            • type: "text_editor_code_execution_create_result"

            • is_file_update: boolean

          • TextEditorCodeExecutionStrReplaceResultBlockParam object

            • type: "text_editor_code_execution_str_replace_result"

            • lines: optional array of string or null

            • new_lines: optional number or null

            • new_start: optional number or null

            • old_lines: optional number or null

            • old_start: optional number or null

        • tool_use_id: string

          pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

      • ToolSearchToolResultBlockParam object

        • type: "tool_search_tool_result"

        • content: ToolSearchToolResultErrorParam or ToolSearchToolSearchResultBlockParam

          • ToolSearchToolResultErrorParam object

            • type: "tool_search_tool_result_error"

            • error_code: ToolSearchToolResultErrorCode

              • "invalid_tool_input"

              • "unavailable"

              • "too_many_requests"

              • "execution_time_exceeded"

            • error_message: optional string or null

          • ToolSearchToolSearchResultBlockParam object

            • type: "tool_search_tool_search_result"

            • tool_references: array of ToolReferenceBlockParam

              • type: "tool_reference"

              • tool_name: string

                maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$

              • cache_control: optional CacheControlEphemeral or null

                Create a cache control breakpoint at this content block.

        • tool_use_id: string

          pattern: ^srvtoolu_[a-zA-Z0-9_]+$

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

      • ContainerUploadBlockParam object

        A content block that represents a file to be uploaded to the container Files uploaded via this block will be available in the container's input directory.

        • type: "container_upload"

        • file_id: string

        • cache_control: optional CacheControlEphemeral or null

          Create a cache control breakpoint at this content block.

  • role: "user" or "assistant" or "system"

    • "user"

    • "assistant"

    • "system"

• model: Model

  The model that will complete your prompt.

  See models for additional details and options.

  • "claude-fable-5-1" or "claude-mythos-5-1" or "claude-sonnet-5" or 14 more

    The model that will complete your prompt.

    See models for additional details and options.

    • "claude-fable-5-1"

      Frontier intelligence for ambitious tasks across coding, scientific discovery, and enterprise workflows

    • "claude-mythos-5-1"

      Our most capable model for cybersecurity and biology research, available through trusted access programs

    • "claude-sonnet-5"

      High-performance model for coding and agents

    • "claude-fable-5"

      Next generation of intelligence for the hardest knowledge work and coding problems

    • "claude-mythos-5"

      Most capable model for cybersecurity and biology research

    • "claude-opus-5"

      Powerful intelligence for long-running agents and coding

    • "claude-opus-4-8"

      Powerful intelligence for long-running agents and coding

    • "claude-opus-4-7"

      Powerful intelligence for long-running agents and coding

    • "claude-mythos-preview"

      New class of intelligence, strongest in coding and cybersecurity

    • "claude-opus-4-6"

      Powerful intelligence for long-running agents and coding

    • "claude-sonnet-4-6"

      Best combination of speed and intelligence

    • "claude-haiku-4-5"

      Fastest model with near-frontier intelligence

    • "claude-haiku-4-5-20251001"

      Fastest model with near-frontier intelligence

    • "claude-opus-4-5"

      Powerful intelligence for long-running agents and coding

    • "claude-opus-4-5-20251101"

      Powerful intelligence for long-running agents and coding

    • "claude-sonnet-4-5"

      High-performance model for agents and coding

    • "claude-sonnet-4-5-20250929"

      High-performance model for agents and coding

  • string

• cache_control: optional CacheControlEphemeral or null

  Top-level cache control automatically applies a cache_control marker to the last cacheable block in the request.

• output_config: optional OutputConfig

  Configuration options for the model's output, such as the output format.

  • effort: optional "low" or "medium" or "high" or 2 more or null

    All possible effort levels.

    • "low"

    • "medium"

    • "high"

    • "xhigh"

    • "max"

  • format: optional JSONOutputFormat or null

    A schema to specify Claude's output format in responses. See structured outputs

    • type: "json_schema"

    • schema: map[unknown]

      The JSON schema of the format

• system: optional string or array of TextBlockParam

  System prompt.

  A system prompt is a way of providing context and instructions to Claude, such as specifying a particular goal or role. See our guide to system prompts.

  • string

  • array of TextBlockParam

    • type: "text"

    • text: string

      minLength: 1

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • citations: optional array of TextCitationParam or null

• thinking: optional ThinkingConfigParam

  Configuration for enabling Claude's extended thinking.

  When enabled, responses include thinking content blocks showing Claude's thinking process before the final answer. Requires a minimum budget of 1,024 tokens and counts towards your max_tokens limit.

  See extended thinking for details.

  • ThinkingConfigEnabled object

    • type: "enabled"

    • budget_tokens: number

      Determines how many tokens Claude can use for its internal reasoning process. Larger budgets can enable more thorough analysis for complex problems, improving response quality.

      Must be ≥1024 and less than max_tokens.

      See extended thinking for details.

      minimum: 1024

    • display: optional "summarized" or "omitted" or null

      Controls how thinking content appears in the response. When set to summarized, thinking is returned normally. When set to omitted, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to summarized.

      • "summarized"

      • "omitted"

  • ThinkingConfigDisabled object

    • type: "disabled"

  • ThinkingConfigAdaptive object

    • type: "adaptive"

    • display: optional "summarized" or "omitted" or null

      Controls how thinking content appears in the response. When set to summarized, thinking is returned normally. When set to omitted, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to summarized.

      • "summarized"

      • "omitted"

• tool_choice: optional ToolChoice

  How the model should use the provided tools. The model can use a specific tool, any available tool, decide by itself, or not use tools at all.

  • ToolChoiceAuto object

    The model will automatically decide whether to use tools.

    • type: "auto"

    • disable_parallel_tool_use: optional boolean

      Whether to disable parallel tool use.

      Defaults to false. If set to true, the model will output at most one tool use.

  • ToolChoiceAny object

    The model will use any available tools.

    • type: "any"

    • disable_parallel_tool_use: optional boolean

      Whether to disable parallel tool use.

      Defaults to false. If set to true, the model will output exactly one tool use.

  • ToolChoiceTool object

    The model will use the specified tool with tool_choice.name.

    • type: "tool"

    • name: string

      The name of the tool to use.

    • disable_parallel_tool_use: optional boolean

      Whether to disable parallel tool use.

      Defaults to false. If set to true, the model will output exactly one tool use.

  • ToolChoiceNone object

    The model will not be allowed to use tools.

    • type: "none"

• tools: optional array of MessageCountTokensTool

  Definitions of tools that the model may use.

  If you include tools in your API request, the model may return tool_use content blocks that represent the model's use of those tools. You can then run those tools using the tool input generated by the model and then optionally return results back to the model using tool_result content blocks.

  There are two types of tools: client tools and server tools. The behavior described below applies to client tools. For server tools, see their individual documentation as each has its own behavior (e.g., the web search tool).

  Each tool definition includes:

  • name: Name of the tool.
  • description: Optional, but strongly-recommended description of the tool.
  • input_schema: JSON schema for the tool input shape that the model will produce in tool_use output content blocks.

  For example, if you defined tools as:

  [
    {
      "name": "get_stock_price",
      "description": "Get the current stock price for a given ticker symbol.",
      "input_schema": {
        "type": "object",
        "properties": {
          "ticker": {
            "type": "string",
            "description": "The stock ticker symbol, e.g. AAPL for Apple Inc."
          }
        },
        "required": ["ticker"]
      }
    }
  ]

  And then asked the model "What's the S&P 500 at today?", the model might produce tool_use content blocks in the response like this:

  [
    {
      "type": "tool_use",
      "id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
      "name": "get_stock_price",
      "input": { "ticker": "^GSPC" }
    }
  ]

  You might then run your get_stock_price tool with \{"ticker": "^GSPC"\} as an input, and return the following back to the model in a subsequent user message:

  [
    {
      "type": "tool_result",
      "tool_use_id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
      "content": "259.75 USD"
    }
  ]

  Tools can be used for workflows that include running client-side tools and functions, or more generally whenever you want the model to produce a particular JSON structure of output.

  See our guide for more details.

  • Tool object

    • type: optional "custom" or null

    • input_schema: object

      JSON schema for this tool's input.

      This defines the shape of the input that your tool accepts and that the model will produce.

      • type: "object"

      • properties: optional map[unknown] or null

      • required: optional array of string or null

    • name: string

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

      maxLength: 128, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,128}$

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • description: optional string

      Description of what this tool does.

      Tool descriptions should be as detailed as possible. The more information that the model has about what the tool is and how to use it, the better it will perform. You can use natural language descriptions to reinforce important aspects of the tool input JSON schema.

    • eager_input_streaming: optional boolean or null

      Enable eager input streaming for this tool. When true, tool input parameters will be streamed incrementally as they are generated, and types will be inferred on-the-fly rather than buffering the full JSON output. When false, streaming is disabled for this tool even if the fine-grained-tool-streaming beta is active. When null (default), uses the default behavior based on beta headers.

    • input_examples: optional array of map[unknown]

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • ToolBash20250124 object

    • type: "bash_20250124"

    • name: "bash"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • input_examples: optional array of map[unknown]

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • CodeExecutionTool20250522 object

    • type: "code_execution_20250522"

    • name: "code_execution"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • CodeExecutionTool20250825 object

    • type: "code_execution_20250825"

    • name: "code_execution"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • CodeExecutionTool20260120 object

    Code execution tool with REPL state persistence (daemon mode + gVisor checkpoint).

    • type: "code_execution_20260120"

    • name: "code_execution"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • CodeExecutionTool20260521 object

    Code execution tool with REPL state persistence.

    • type: "code_execution_20260521"

    • name: "code_execution"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • BrowserToolset20260801 object

    The browser toolset: a single tools[] entry (carrying no name) that declares the browser tool family. The model is served the family's tool with any members disabled via configs removed from its schema.

    • type: "browser_toolset_20260801"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • configs: optional BrowserToolsetConfigs or null

      Per-member configuration for browser_toolset_20260801: one optional field per member tool, keyed by the member name — the same name the member's tool_use blocks carry. Every member is an accepted key, and a member's defaults apply wherever its key is absent. Unknown keys are rejected: the field set is this toolset version's complete member set.

      • type: optional BrowserTypeConfig or null

        type's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • close_tab: optional BrowserCloseTabConfig or null

        close_tab's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • double_click: optional BrowserDoubleClickConfig or null

        double_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • file_upload: optional BrowserFileUploadConfig or null

        file_upload's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • find: optional BrowserFindConfig or null

        find's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • form_input: optional BrowserFormInputConfig or null

        form_input's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • get_page_text: optional BrowserGetPageTextConfig or null

        get_page_text's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • hold_key: optional BrowserHoldKeyConfig or null

        hold_key's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • hover: optional BrowserHoverConfig or null

        hover's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • javascript_exec: optional BrowserJavascriptExecConfig or null

        javascript_exec's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • key: optional BrowserKeyConfig or null

        key's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_click: optional BrowserLeftClickConfig or null

        left_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_click_drag: optional BrowserLeftClickDragConfig or null

        left_click_drag's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_mouse_down: optional BrowserLeftMouseDownConfig or null

        left_mouse_down's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_mouse_up: optional BrowserLeftMouseUpConfig or null

        left_mouse_up's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • list_tabs: optional BrowserListTabsConfig or null

        list_tabs's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • middle_click: optional BrowserMiddleClickConfig or null

        middle_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • mouse_move: optional BrowserMouseMoveConfig or null

        mouse_move's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • navigate: optional BrowserNavigateConfig or null

        navigate's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • new_tab: optional BrowserNewTabConfig or null

        new_tab's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • read_console: optional BrowserReadConsoleConfig or null

        read_console's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • read_network: optional BrowserReadNetworkConfig or null

        read_network's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • read_page: optional BrowserReadPageConfig or null

        read_page's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • right_click: optional BrowserRightClickConfig or null

        right_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • screenshot: optional BrowserScreenshotConfig or null

        screenshot's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • scroll: optional BrowserScrollConfig or null

        scroll's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • scroll_to: optional BrowserScrollToConfig or null

        scroll_to's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • switch_tab: optional BrowserSwitchTabConfig or null

        switch_tab's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • triple_click: optional BrowserTripleClickConfig or null

        triple_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • wait: optional BrowserWaitConfig or null

        wait's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • zoom: optional BrowserZoomConfig or null

        zoom's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

  • MemoryTool20250818 object

    • type: "memory_20250818"

    • name: "memory"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • input_examples: optional array of map[unknown]

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • ComputerToolset20260801 object

    The computer toolset: a single tools[] entry (carrying no name) that declares the computer tool family. The model is served the family's tool with any members disabled via configs removed from its schema. Every member is enabled by default, zoom included. The single-tool options display_number and enable_zoom are not fields of a toolset entry — it carries only type, configs, and cache_control; zoom is controlled via configs.zoom.enabled.

    • type: "computer_toolset_20260801"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • configs: optional ComputerToolsetConfigs or null

      Per-member configuration for computer_toolset_20260801: one optional field per member tool, keyed by the member name — the same name the member's tool_use blocks carry. Every member is an accepted key, and a member's defaults apply wherever its key is absent. Unknown keys are rejected: the field set is this toolset version's complete member set.

      • type: optional ComputerTypeConfig or null

        type's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • cursor_position: optional ComputerCursorPositionConfig or null

        cursor_position's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • double_click: optional ComputerDoubleClickConfig or null

        double_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • hold_key: optional ComputerHoldKeyConfig or null

        hold_key's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • key: optional ComputerKeyConfig or null

        key's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_click: optional ComputerLeftClickConfig or null

        left_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_click_drag: optional ComputerLeftClickDragConfig or null

        left_click_drag's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_mouse_down: optional ComputerLeftMouseDownConfig or null

        left_mouse_down's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • left_mouse_up: optional ComputerLeftMouseUpConfig or null

        left_mouse_up's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • middle_click: optional ComputerMiddleClickConfig or null

        middle_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • mouse_move: optional ComputerMouseMoveConfig or null

        mouse_move's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • right_click: optional ComputerRightClickConfig or null

        right_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • screenshot: optional ComputerScreenshotConfig or null

        screenshot's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • scroll: optional ComputerScrollConfig or null

        scroll's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • triple_click: optional ComputerTripleClickConfig or null

        triple_click's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • wait: optional ComputerWaitConfig or null

        wait's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

      • zoom: optional ComputerZoomConfig or null

        zoom's config overrides.

        • defer_loading: optional boolean or null

          Defer loading for this member. Must resolve to the same value on every enabled member of the toolset.

        • enabled: optional boolean or null

          Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema.

  • ToolTextEditor20250124 object

    • type: "text_editor_20250124"

    • name: "str_replace_editor"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • input_examples: optional array of map[unknown]

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • ToolTextEditor20250429 object

    • type: "text_editor_20250429"

    • name: "str_replace_based_edit_tool"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • input_examples: optional array of map[unknown]

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • ToolTextEditor20250728 object

    • type: "text_editor_20250728"

    • name: "str_replace_based_edit_tool"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • input_examples: optional array of map[unknown]

    • max_characters: optional number or null

      Maximum number of characters to display when viewing a file. If not specified, defaults to displaying the full file.

      minimum: 1

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • WebSearchTool20250305 object

    • type: "web_search_20250305"

    • name: "web_search"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • allowed_domains: optional array of string or null

      If provided, only these domains will be included in results. Cannot be used alongside blocked_domains.

    • blocked_domains: optional array of string or null

      If provided, these domains will never appear in results. Cannot be used alongside allowed_domains.

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • max_uses: optional number or null

      Maximum number of times the tool can be used in the API request.

      exclusiveMinimum: 0

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

    • user_location: optional UserLocation or null

      Parameters for the user's location. Used to provide more relevant search results.

      • type: "approximate"

      • city: optional string or null

        The city of the user.

        maxLength: 255, minLength: 1

      • country: optional string or null

        The two letter ISO country code of the user.

        maxLength: 2, minLength: 2

      • region: optional string or null

        The region of the user.

        maxLength: 255, minLength: 1

      • timezone: optional string or null

        The IANA timezone of the user.

        maxLength: 255, minLength: 1

  • WebFetchTool20250910 object

    • type: "web_fetch_20250910"

    • name: "web_fetch"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • allowed_domains: optional array of string or null

      List of domains to allow fetching from

    • blocked_domains: optional array of string or null

      List of domains to block fetching from

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • citations: optional CitationsConfigParam or null

      Citations configuration for fetched documents. Citations are disabled by default.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • max_content_tokens: optional number or null

      Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.

      exclusiveMinimum: 0

    • max_uses: optional number or null

      Maximum number of times the tool can be used in the API request.

      exclusiveMinimum: 0

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • WebSearchTool20260209 object

    • type: "web_search_20260209"

    • name: "web_search"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • allowed_domains: optional array of string or null

      If provided, only these domains will be included in results. Cannot be used alongside blocked_domains.

    • blocked_domains: optional array of string or null

      If provided, these domains will never appear in results. Cannot be used alongside allowed_domains.

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • max_uses: optional number or null

      Maximum number of times the tool can be used in the API request.

      exclusiveMinimum: 0

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

    • user_location: optional UserLocation or null

      Parameters for the user's location. Used to provide more relevant search results.

  • WebFetchTool20260209 object

    • type: "web_fetch_20260209"

    • name: "web_fetch"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • allowed_domains: optional array of string or null

      List of domains to allow fetching from

    • blocked_domains: optional array of string or null

      List of domains to block fetching from

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • citations: optional CitationsConfigParam or null

      Citations configuration for fetched documents. Citations are disabled by default.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • max_content_tokens: optional number or null

      Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.

      exclusiveMinimum: 0

    • max_uses: optional number or null

      Maximum number of times the tool can be used in the API request.

      exclusiveMinimum: 0

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • WebFetchTool20260309 object

    Web fetch tool with use_cache parameter for bypassing cached content.

    • type: "web_fetch_20260309"

    • name: "web_fetch"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • allowed_domains: optional array of string or null

      List of domains to allow fetching from

    • blocked_domains: optional array of string or null

      List of domains to block fetching from

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • citations: optional CitationsConfigParam or null

      Citations configuration for fetched documents. Citations are disabled by default.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • max_content_tokens: optional number or null

      Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.

      exclusiveMinimum: 0

    • max_uses: optional number or null

      Maximum number of times the tool can be used in the API request.

      exclusiveMinimum: 0

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

    • use_cache: optional boolean

      Whether to use cached content. Set to false to bypass the cache and fetch fresh content. Only set to false when the user explicitly requests fresh content or when fetching rapidly-changing sources.

  • WebSearchTool20260318 object

    • type: "web_search_20260318"

    • name: "web_search"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • allowed_domains: optional array of string or null

      If provided, only these domains will be included in results. Cannot be used alongside blocked_domains.

    • blocked_domains: optional array of string or null

      If provided, these domains will never appear in results. Cannot be used alongside allowed_domains.

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • max_uses: optional number or null

      Maximum number of times the tool can be used in the API request.

      exclusiveMinimum: 0

    • response_inclusion: optional "full" or "excluded"

      How this tool's result blocks appear in the API response when the result was consumed by a completed code_execution call in the same turn. 'full' returns the complete content (default). 'excluded' drops the nested server_tool_use and result block pair entirely. Results from direct calls, or from code_execution calls that paused before completing, are always returned in full so they can be sent back on the next turn.

      • "full"

      • "excluded"

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

    • user_location: optional UserLocation or null

      Parameters for the user's location. Used to provide more relevant search results.

  • WebFetchTool20260318 object

    • type: "web_fetch_20260318"

    • name: "web_fetch"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • allowed_domains: optional array of string or null

      List of domains to allow fetching from

    • blocked_domains: optional array of string or null

      List of domains to block fetching from

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • citations: optional CitationsConfigParam or null

      Citations configuration for fetched documents. Citations are disabled by default.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • max_content_tokens: optional number or null

      Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.

      exclusiveMinimum: 0

    • max_uses: optional number or null

      Maximum number of times the tool can be used in the API request.

      exclusiveMinimum: 0

    • response_inclusion: optional "full" or "excluded"

      How this tool's result blocks appear in the API response when the result was consumed by a completed code_execution call in the same turn. 'full' returns the complete content (default). 'excluded' drops the nested server_tool_use and result block pair entirely. Results from direct calls, or from code_execution calls that paused before completing, are always returned in full so they can be sent back on the next turn.

      • "full"

      • "excluded"

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

    • use_cache: optional boolean

      Whether to use cached content. Set to false to bypass the cache and fetch fresh content. Only set to false when the user explicitly requests fresh content or when fetching rapidly-changing sources.

  • ToolSearchToolBm25_20251119 object

    • type: "tool_search_tool_bm25_20251119" or "tool_search_tool_bm25"

      • "tool_search_tool_bm25_20251119"

      • "tool_search_tool_bm25"

    • name: "tool_search_tool_bm25"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs

  • ToolSearchToolRegex20251119 object

    • type: "tool_search_tool_regex_20251119" or "tool_search_tool_regex"

      • "tool_search_tool_regex_20251119"

      • "tool_search_tool_regex"

    • name: "tool_search_tool_regex"

      Name of the tool.

      This is how the tool will be called by the model and in tool_use blocks.

    • allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"

      • "direct"

      • "code_execution_20250825"

      • "code_execution_20260120"

      • "code_execution_20260521"

    • cache_control: optional CacheControlEphemeral or null

      Create a cache control breakpoint at this content block.

    • defer_loading: optional boolean

      If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search.

    • strict: optional boolean

      When true, guarantees schema validation on tool names and inputs