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.
`tools`	`tool[]`	Two tool types have an effect. A `web_search` tool’s `filters` (`allowed_domains`, `blocked_domains`) restrict the domains searched, read, and cited (see Web Search Tool); at most one per request. An `mcp` tool gives the model a remote MCP server to call (see MCP Tools); at most 10 per request. Every other tool is accepted and ignored.
`data_sources`	`{"free": string[], "pay_per_use": string[]}`	Parallel extension. Data Connectors to query in addition to the web, for `medium` and `high` effort (see Data Connectors). With the OpenAI Python SDK, pass it in `extra_body`.

Accepted but ignored (for SDK compatibility)

tool_choice, parallel_tool_calls, temperature, top_p, max_output_tokens, truncation, store, user, include, any tool other than web_search and mcp, the web_search tool’s search_context_size and user_location, and the mcp tool’s server_description. 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. Grounding is automatic, so a web_search tool without filters changes nothing. 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, tool_choice: "auto"), not the values you sent. tools echoes your web_search tool as you sent it, including its ignored search_context_size and user_location, and your mcp tools with headers and authorization removed and any server_url query string masked. It is [] when you sent neither.

Rejected

Request	Status	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’.”
More than one `web_search` tool	`400`	”tools may contain at most one web_search tool.”
Malformed `web_search` tool (`filters` not an object, unknown filter key)	`400`	”Request validation error. […]”
Domain filter entry with a scheme, port, query string, or fragment	`400`	”Invalid source filter(s) in source_policy: […]. Expected format: plain domains (e.g., example.com, subdomain.example.gov) or bare domain extension starting with a period (e.g., .gov, .edu, .co.uk). […]”
More than 200 domain filter entries	`400`	”Total number of source filters in source_policy cannot exceed 200.”
Same entry in `allowed_domains` and `blocked_domains`	`400`	”include_domains and exclude_domains cannot have overlapping entries.”
`mcp` tool without `require_approval: "never"` (omitted, `"always"`, or an object)	`400`	”Request validation error. […]”
`mcp` tool without `server_url`, with a blank `server_label`, or with `connector_id`, `tunnel_id`, or `defer_loading`	`400`	”Request validation error. […]”
`mcp` tool with `allowed_tools` as a filter object	`400`	”Request validation error. […]”
`mcp` tool with `allowed_tools: []`	`400`	”MCP server configuration requires either null or a non-empty list of allowed tools.”
More than 10 `mcp` tools	`400`	”Number of MCP servers provided (11) exceeds the maximum allowed limit of 10.”
`data_sources` with `reasoning.effort: "low"`	`400`	”data_sources requires reasoning.effort=‘medium’ or ‘high’.”
`data_sources` connector name that is unknown, in the wrong list, or an Index Partner	`400`	”Request validation error. […] Unknown data partner(s) in pay_per_use: […]”
`data_sources` connector not yet available to your organization	`400`	”Selected data provider(s) are unavailable: […]. Available: […].”
`data_sources` connector with the same name as an `mcp` tool’s `server_label`	`400`	”Selected data provider names collide with mcp_servers names: […].”
`additional_data_providers` (retired)	`400`	”Request validation error. […] additional_data_providers was replaced by data_sources […]”

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, read by `type`: one `web_search_call` item per search the model ran or page it read (see Web Search Tool), one `mcp_list_tools` item per MCP server reported and one `mcp_call` item per MCP tool call (see MCP Tools), and the `message` item whose `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.
`tools`	Your `web_search` and `mcp` tools, echoed back with MCP credentials removed; `[]` otherwise.

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