Example

Call startup() early, for example on application boot, then call .query() on the returned handle once a prompt is ready. This moves subprocess spawn and initialization out of the critical path.

import { startup } from "@anthropic-ai/claude-agent-sdk";

// Pay startup cost upfront
const warm = await startup({ options: { maxTurns: 3 } });

// Later, when a prompt is ready, this is immediate
for await (const message of warm.query("What files are here?")) {
  console.log(message);
}

tool()

Creates a type-safe MCP tool definition for use with SDK MCP servers.

function tool<Schema extends AnyZodRawShape>(
  name: string,
  description: string,
  inputSchema: Schema,
  handler: (args: InferShape<Schema>, extra: unknown) => Promise<CallToolResult>,
  extras?: { annotations?: ToolAnnotations; searchHint?: string; alwaysLoad?: boolean }
): SdkMcpToolDefinition<Schema>;