Example

{
    "event_id": "event_6202",
    "type": "response.mcp_call_arguments.done",
    "response_id": "resp_001",
    "item_id": "mcp_call_001",
    "output_index": 0,
    "arguments": "{\"q\":\"docs\"}"
}

response.mcp_call.in_progress

Returned when an MCP tool call has started and is in progress.