Language (chat)

Text in, text out, with image inputs where the model is a vision-language model. The one task that does not go through the task API or the SDK.

• OpenAI's chat completion body: model, messages, stream, and the accepted fields of the chat completions reference.
• image_url parts in a user message on a model advertising vision; input_audio and file parts are refused (audio goes through the task API).
• Tool calls, json_object and json_schema outputs, logprobs and reasoning_effort where the model advertises the feature; otherwise a 400 unsupported_parameter.

• input_output_tokens: prompt_tokens and completion_tokens at the model's separate input and output rates, counted by the serving engine's tokenizer for the pinned model.
• With image inputs, tokens under the model's image-token rule; image count and dimensions change the charge.
• The charge is x-hips-cost-micros, or on a stream the hips object of the final usage chunk.

• OpenAI's chat.completion object; id is the request id. finish_reason is stop, length or tool_calls; content_filter is never emitted.
• Streamed: one data: line per chunk, a final usage chunk with stream_options.include_usage, then data: [DONE]. A failure after the stream started is one data: line with the error envelope and no [DONE].