This API is in beta stage and may have breaking changes.
The Responses API Beta supports comprehensive tool calling capabilities, allowing models to call functions, execute tools in parallel, and handle complex multi-step workflows.
Define tools using the OpenAI function calling format:
Control when and how tools are called:
Define multiple tools for complex workflows:
The API supports parallel execution of multiple tools:
When tools are called, the response includes function call information:
Include tool responses in follow-up requests:
The id field is required for function_call_output objects when including tool responses in conversation history.
Monitor tool calls in real-time with streaming:
Ensure tool calls have proper structure:
Required fields:
type: Always “function_call”id: Unique identifier for the function call objectname: Function name matching tool definitionarguments: Valid JSON string with function parameterscall_id: Unique identifier for the call