Create a chat completion

Sends a conversation to a chat model and returns its reply. Set stream: true to receive server-sent events; the last chunk before [DONE] carries usage.

Authentication

AuthorizationBearer

Your API key, sk-..., from Console → API keys.

Request

This endpoint expects an object.

modelstringRequired

The model id, lab/model.

messageslist of objectsRequired

The conversation so far.

streambooleanOptionalDefaults to false

Send the reply as server-sent events.

stream_optionsobjectOptional

Streaming options. Usage is always sent at the end of a stream.

max_tokensintegerOptional>=1

The most output tokens to produce. Keeps the hold on your balance small.

max_completion_tokensintegerOptional>=1

Same as max_tokens, including reasoning tokens.

temperaturedoubleOptional0-2

top_pdoubleOptional0-1

frequency_penaltydoubleOptional-2-2

presence_penaltydoubleOptional-2-2

stopstring or list of stringsOptional

Up to 4 sequences where the model stops.

seedintegerOptional

nintegerOptional1-8Defaults to 1

How many replies to make. Each is held for its full output.

logprobsbooleanOptional

top_logprobsintegerOptional0-20

logit_biasmap from strings to doublesOptional

toolslist of objectsOptional

Functions the model may call. Only function tools are kept.

tool_choiceenum or objectOptional

auto, none, required, or a specific function.

parallel_tool_callsbooleanOptional

response_formatobjectOptional

{"type": "json_object"} or {"type": "json_schema", "json_schema": {...}}.

reasoning_effortenumOptional

How much a reasoning model thinks, on models that support it.

Allowed values:

userstringOptional

Your own id for the end user.

metadatamap from strings to stringsOptional

Response

The model’s reply, or a stream of chunks when stream is true.

idstringOptional

objectenumOptional

Allowed values:

createdintegerOptional

modelstringOptional

choiceslist of objectsOptional

usageobjectOptional

Errors

400

Bad Request Error

401

Unauthorized Error

402

Payment Required Error

403

Forbidden Error

404

Not Found Error

429

Too Many Requests Error

502

Bad Gateway Error

503

Service Unavailable Error