An agent built on OpenAI's Responses API needs to look up two independent pieces of information in a single turn, using the same tool twice with different arguments. According to OpenAI's documentation, how does the API support this, and what must the client do in response?
- a single assistant turn can never include more than one function call; the model must wait for the client to answer the first call before it is permitted to request the second one
- the client may return one combined `function_call_output` message covering every function call made in that turn, as long as the message lists all of the relevant call IDs together
- `parallel_tool_calls` can only ever be set to true, since the API provides no way to restrict a response to at most one function call per turn
- a single assistant turn can include multiple function calls, each carrying its own `call_id`, and the client must send back one `function_call_output` item per `call_id` containing that call's result; setting `parallel_tool_calls` to false instead restricts the model to at most one function call per turn
Why D? And why not the others?
Correct answer: D. a single assistant turn can include multiple function calls, each carrying its own `call_id`, and the client must send back one `function_call_output` item per `call_id` containing that call's result; setting `parallel_tool_calls` to false instead restricts the model to at most one function call per turn
OpenAI's documentation states that the model may call multiple functions in a single turn, with the response's output array containing a separate entry, each with its own `call_id`, for every distinct function invocation, and that the client must process each one independently and return a separate `function_call_output` message per `call_id` rather than merging them; it also documents `parallel_tool_calls` as a request parameter that, when set to false, restricts the model to exactly zero or one function call per turn. The option denying multiple calls per turn contradicts the documented multi-call output shape directly. The option allowing a single combined output message is wrong because the documented pattern matches results back to individual call IDs one at a time, not as a bundled response. The option claiming `parallel_tool_calls` cannot be disabled is wrong because the documented false setting exists specifically to enforce a single-call-per-turn restriction.
Source: OpenAI, Function calling guide, https://developers.openai.com/api/docs/guides/function-calling