Addendum — echoed request configuration fields also present on the Response object
(these are returned so clients can introspect how the response was configured)
model: string # required [model used to generate the response; echo of request]
instructions: string | array | null # required [system/developer instructions used for this response; echo of request]
tools: array # required [tool definitions provided to the model; echo of request]
tool_choice: string | object # required [tool selection mode / constraints; echo of request]
metadata: object | null # required [developer metadata map; echo of request]
temperature: number | null # required [sampling temperature; echo of request]
top_p: number | null # required [nucleus sampling; echo of request]
parallel_tool_calls: boolean # required [whether tool calls may run in parallel; echo of request]
conversation: object | null # optional [conversation association; if present contains `{ id: string }` matching the request]
previous_response_id: string | null # optional [multi-turn linkage; echo of request]
top_logprobs: integer | null # optional [how many per-token alternatives to return; echo of request]
reasoning: object | null # optional [reasoning configuration; echo of request]
background: boolean | null # optional [background processing requested; echo of request]
max_output_tokens: integer | null # optional [output token cap; echo of request]
max_tool_calls: integer | null # optional [tool-call cap; echo of request]
text: object | null # optional [text output formatting config; echo of request]
prompt: object | null # optional [prompt template reference; echo of request]
truncation: "auto" | "disabled" | null # optional [truncation strategy; echo of request]
safety_identifier: string # optional [stable safety identifier; echo of request]
prompt_cache_key: string # optional [prompt caching key; echo of request]
prompt_cache_retention: "in-memory" | "24h" | null # optional [prompt cache retention policy; echo of request]
user: string # optional [deprecated stable end-user identifier; echo of request]
service_tier: "auto" | "default" | "flex" | "scale" | "priority" | null # optional [requested tier; response may reflect actual tier used]
Note: this is not the “Open Responses” new spec - this is the API.