OpenAI Responses Compatibility

The Responses API models the canonical OpenAI Responses request (POST https://api.parallel.ai/v1/responses), so a stock openai SDK client works by changing only base_url, api_key, and model. This page documents exactly which fields are honored, which are accepted for SDK compatibility but ignored, and which are rejected.

Request fields

Honored

Field	Type	Meaning
`model`	`string`	Must be `"parallel"` — the only model. The tier is chosen via `reasoning.effort`.
`input`	`string` \| `message[]`	The question, or a list of `{role, content}` messages. Text only. Must be non-empty and contain at least one `user` message.
`reasoning`	`{"effort": "low" \| "medium" \| "high"}`	Selects the tier. Defaults to `medium`.
`instructions`	`string`	System instructions prepended to the request.
`text`	`object`	Text-output config, including structured output — structured content is returned JSON-encoded in the output text.
`stream`	`boolean`	SSE streaming. The answer currently arrives as a single text delta, not token-by-token.
`previous_response_id`	`string`	Prior response id, for multi-turn context.
`metadata`	`{string: string}`	Arbitrary tags echoed back on the response. Max 16 keys, ≤64 chars/key, ≤512 chars/value.

Accepted but ignored (for SDK compatibility)

tools, tool_choice, parallel_tool_calls, temperature, top_p, max_output_tokens, truncation, store, user, include. These are part of the OpenAI contract so a stock SDK client’s payload never fails validation, but the backend does not act on them today. Notably you do not pass tools: [{"type": "web_search"}] — grounding is automatic. store is likewise ignored: responses are always stored so they can be referenced via previous_response_id (see Statefulness). Unknown top-level fields are silently dropped, so newer OpenAI SDK versions won’t break.

Ignored fields come back on the response object with their default values (temperature: null, tools: [], tool_choice: "auto"), not the values you sent.

Rejected

Request	Error
`background: true`	`400` — “background mode is not supported on /v1/responses; submit long-running work via the Task API (POST /v1/tasks/runs) instead.”
Non-text (multimodal) input parts	`400` — “input contains unsupported non-text content parts: input_image (this endpoint only accepts text input today)“
Empty `input`	`400` — “input must not be empty.”
`input` with no `user` message	`400` — “input must contain at least one user message.”
Any `model` other than `parallel`	`400` — “The Responses API only supports model ‘parallel’.”

Errors use the standard OpenAI error envelope:

{
  "error": {
    "message": "The Responses API only supports model 'parallel'.",
    "type": "invalid_request_error",
    "param": null,
    "code": null
  }
}

Requests over your quota return 429 — back off and retry, and see rate limits for current limits.

Response fields

A standard OpenAI Responses object. The fields you’ll typically read:

Field	Meaning
`output_text`	The final answer string (SDK convenience accessor).
`output[]`	Output items; the `message` item’s `content[]` carries the answer text.
`usage`	Token counts (`input_tokens`, `output_tokens`, `total_tokens`).
`id`	Response id — pass as `previous_response_id` for follow-ups.
`metadata`	Your request metadata, echoed back.

reasoning and text are echoed as null on the response even when they were sent and honored — read the tier from your request, not the response. Source citations are returned as url_citation annotations on the output text — see Citations.

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OpenAI Responses Compatibility

Request fields

Honored

Accepted but ignored (for SDK compatibility)

Rejected

Response fields

​Request fields

​Honored

​Accepted but ignored (for SDK compatibility)

​Rejected

​Response fields

Request fields

Honored

Accepted but ignored (for SDK compatibility)

Rejected

Response fields