Send a JSON request to POST /v1/responses with Authorization: Bearer YOUR_API_KEY.

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Parameters

ParameterRequiredMeaning
modelYesExact currently available model ID.
inputNoText or supported multimodal input.
instructionsNoSystem-level instructions controlling the model’s role or behavior.
previous_response_idNoPrevious response ID, only where the selected model and route support continuation. Context billing also depends on that route.
truncationNoTruncation policy: auto or disabled, where supported.
Responses compatibility does not guarantee that every model supports every tool, reasoning setting, or continuation feature. Check Model Square, then test the exact capability your application needs. For the Codex client, see Codex setup. For message-based clients, see Chat Completions.