curl -X POST 'https://api.openai.com/v1/chat/completions' \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "messages": [
    {
      "content": "example-content",
      "role": "developer",
      "name": "example-name"
    }
  ],
  "model": "gpt-6-astra"
}'

# POST /chat/completions (OpenAI API)
Base URL: https://api.openai.com/v1
Auth: Authorization; OpenAI API key; required.
Request formats: application/json.
Last verified: 2026-10-20

> Create chat completion

## Critical Gotchas
* The Responses API is the primary interface for new text and tool workflows; Chat Completions remains a separate compatibility API.
* Audio transcription uploads use multipart form data rather than a JSON request body.

## cURL
curl -X POST 'https://api.openai.com/v1/chat/completions' \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "messages": [
    {
      "content": "example-content",
      "role": "developer",
      "name": "example-name"
    }
  ],
  "model": "gpt-6-astra"
}'

## Parameters
| Name | In | Type | Required | Description |
| :--- | :--- | :--- | :--- | :--- |
| messages | body | object[] | Yes | A list of messages comprising the conversation so far. Depending on the [mode... |
| model | body | string | Yes | Request body field model. |
| metadata | body | object | No | Set of 16 key-value pairs that can be attached to an object. This can be usef... |
| top_logprobs | body | integer | No | An integer between 0 and 20 specifying the maximum number of most likely toke... |
| temperature | body | number | No | What sampling temperature to use, between 0 and 2. Higher values like 0.8 wil... |
| top_p | body | number | No | An alternative to sampling with temperature, called nucleus sampling, where t... |
| user | body | string | No | This field is being replaced by `safety_identifier` and `prompt_cache_key`. U... |
| safety_identifier | body | string | No | A stable identifier used to help detect users of your application that may be... |
Other params: prompt_cache_key, prompt_cache_retention, prompt_cache_options, service_tier, modalities, verbosity, reasoning_effort, max_completion_tokens, frequency_penalty, presence_penalty, web_search_options, response_format, audio, store, moderation, stream, stop, logit_bias, logprobs, max_tokens, n, prediction, seed, stream_options, tools, tool_choice, parallel_tool_calls, function_call, functions

## Response example
{"id":"string","choices":[{}]}

---
Need an API key? Get one at https://platform.openai.com/api-keys

POST

POST /chat/completions — OpenAI API

OpenAI API key (required); https://api.openai.com/v1

OpenAI API

Create chat completion

Base URL: https://api.openai.com/v1
Auth: Authorization: Bearer <OPENAI_API_KEY>
Last verified: 2026-10-20 · upstream hash matched

Actions Try in browser→

Agents: curl -H "Accept: text/markdown" this URL
→ 440 tokens · Vary: Accept

Critical gotchas

The Responses API is the primary interface for new text and tool workflows; Chat Completions remains a separate compatibility API.

Audio transcription uploads use multipart form data rather than a JSON request body.

cURL

curl -X POST 'https://api.openai.com/v1/chat/completions' \  -H "Authorization: Bearer $OPENAI_API_KEY" \  -H 'Content-Type: application/json' \  -d '{  "messages": [    {      "content": "example-content",      "role": "developer",      "name": "example-name"    }  ],  "model": "gpt-6-astra"}'

Parameters

Name	In	Type	Required	Description
metadata	body	object	No	Set of 16 key-value pairs that can be attached to an object. This can be useful for storing additional information about the object in a structured format, and querying for objects via API or the dashboard. Keys are strings with a maximum length of 64 characters. Values are strings with a maximum length of 512 characters.
top_logprobs	body	integer	No	An integer between 0 and 20 specifying the maximum number of most likely tokens to return at each token position, each with an associated log probability. In some cases, the number of returned tokens may be fewer than requested. `logprobs` must be set to `true` if this parameter is used.
temperature	body	number	No	What sampling temperature to use, between 0 and 2. Higher values like 0.8 will make the output more random, while lower values like 0.2 will make it more focused and deterministic. We generally recommend altering this or `top_p` but not both.
top_p	body	number	No	An alternative to sampling with temperature, called nucleus sampling, where the model considers the results of the tokens with top_p probability mass. So 0.1 means only the tokens comprising the top 10% probability mass are considered. We generally recommend altering this or `temperature` but not both.
user	body	string	No	This field is being replaced by `safety_identifier` and `prompt_cache_key`. Use `prompt_cache_key` instead to maintain caching optimizations. A stable identifier for your end-users. Used to boost cache hit rates by better bucketing similar requests and to help OpenAI detect and prevent abuse. [Learn more](https://developers.openai.com/api/docs/guides/safety-best-practices#implement-safety-identifiers).
safety_identifier	body	string	No	A stable identifier used to help detect users of your application that may be violating OpenAI's usage policies. The IDs should be a string that uniquely identifies each user, with a maximum length of 128 characters. We recommend hashing their username or email address, in order to avoid sending us any identifying information. [Learn more](https://developers.openai.com/api/docs/guides/safety-best-practices#implement-safety-identifiers).
prompt_cache_key	body	string	No	Used by OpenAI to cache responses for similar requests to optimize your cache hit rates. Replaces the `user` field. [Learn more](https://developers.openai.com/api/docs/guides/prompt-caching).
prompt_cache_retention	body	string	No	Deprecated. Use `prompt_cache_options.ttl` instead. The retention policy for the prompt cache. Set to `24h` to enable extended prompt caching, which keeps cached prefixes active for longer, up to a maximum of 24 hours. [Learn more](https://developers.openai.com/api/docs/guides/prompt-caching#prompt-cache-retention). This field expresses a maximum retention policy, while `prompt_cache_options.ttl` expresses a minimum cache lifetime. The two fields are independent and do not interact. For `gpt-5.5`, `gpt-5.5-pro`, and future models, only `24h` is supported. For older models that support both `in_memory` and `24h`, the default depends on your organization's data retention policy: - Organizations without ZDR enabled default to `24h`. - Organizations with ZDR enabled default to `in_memory` when `prompt_cache_retention` is not specified.
prompt_cache_options	body	object	No	Options for prompt caching. Supported for `gpt-5.6` and later models. By default, OpenAI automatically chooses one implicit cache breakpoint. You can add explicit breakpoints to content blocks with `prompt_cache_breakpoint`. Each request can write up to four breakpoints. For cache matching, OpenAI considers up to the latest 80 breakpoints in the conversation, without a content-block lookback limit. Set `mode` to `explicit` to disable the implicit breakpoint. The `ttl` defaults to `30m`, which is currently the only supported value. See the [prompt caching guide](https://developers.openai.com/api/docs/guides/prompt-caching) for current details.
messages	body	object[]	Yes	A list of messages comprising the conversation so far. Depending on the [model](https://developers.openai.com/api/docs/models) you use, different message types (modalities) are supported, like [text](https://developers.openai.com/api/docs/guides/text), [images](https://developers.openai.com/api/docs/guides/images-vision), and [audio](https://developers.openai.com/api/docs/guides/audio).
model	body	string	Yes	Request body field model.
service_tier	body	string	No	Specifies the processing type used for serving the request. - If set to 'auto', then the request will be processed with the service tier configured in the Project settings. Unless otherwise configured, the Project will use 'default'. - If set to 'default', then the request will be processed with the standard pricing and performance for the selected model. - If set to '[flex](https://developers.openai.com/api/docs/guides/flex-processing)', then the request will be processed with the Flex Processing service tier. - To opt-in to [Fast mode](https://developers.openai.com/api/docs/guides/fast-mode) at the request level, include the `service_tier=fast` or `service_tier=priority` parameter for Responses or Chat Completions. The response will show `service_tier=priority` regardless of if you specify `service_tier=fast` or `priority` in your request. - When not set, the default behavior is 'auto'. When the `service_tier` parameter is set, the response body will include the `service_tier` value based on the processing mode actually used to serve the request. This response value may be different from the value set in the parameter.
modalities	body	string[]	No	Output types that you would like the model to generate. Most models are capable of generating text, which is the default: `["text"]` The `gpt-4o-audio-preview` model can also be used to [generate audio](https://developers.openai.com/api/docs/guides/audio). To request that this model generate both text and audio responses, you can use: `["text", "audio"]`
verbosity	body	string	No	Constrains the verbosity of the model's response. Lower values will result in more concise responses, while higher values will result in more verbose responses. Currently supported values are `low`, `medium`, and `high`. The default is `medium`.
reasoning_effort	body	string	No	Constrains effort on reasoning for reasoning models. Currently supported values are `none`, `minimal`, `low`, `medium`, `high`, `xhigh`, and `max`. Reducing reasoning effort can result in faster responses and fewer tokens used on reasoning in a response. Not all reasoning models support every value. See the [reasoning guide](https://developers.openai.com/api/docs/guides/reasoning) for model-specific support.
max_completion_tokens	body	integer	No	An upper bound for the number of tokens that can be generated for a completion, including visible output tokens and [reasoning tokens](https://developers.openai.com/api/docs/guides/reasoning).
frequency_penalty	body	number	No	Number between -2.0 and 2.0. Positive values penalize new tokens based on their existing frequency in the text so far, decreasing the model's likelihood to repeat the same line verbatim.
presence_penalty	body	number	No	Number between -2.0 and 2.0. Positive values penalize new tokens based on whether they appear in the text so far, increasing the model's likelihood to talk about new topics.
web_search_options	body	object	No	This tool searches the web for relevant results to use in a response. Learn more about the [web search tool](https://developers.openai.com/api/docs/guides/tools-web-search).
response_format	body	object	No	An object specifying the format that the model must output. Setting to `{ "type": "json_schema", "json_schema": {...} }` enables Structured Outputs which ensures the model will match your supplied JSON schema. Learn more in the [Structured Outputs guide](https://developers.openai.com/api/docs/guides/structured-outputs). Setting to `{ "type": "json_object" }` enables the older JSON mode, which ensures the message the model generates is valid JSON. Using `json_schema` is preferred for models that support it.
audio	body	object	No	Parameters for audio output. Required when audio output is requested with `modalities: ["audio"]`. [Learn more](https://developers.openai.com/api/docs/guides/audio).
store	body	boolean	No	Whether or not to store the output of this chat completion request for use in our [model distillation](https://developers.openai.com/api/docs/guides/supervised-fine-tuning#distilling-from-a-larger-model) or [evals](https://developers.openai.com/api/docs/guides/evals) products. Supports text and image inputs. Note: image inputs over 8MB will be dropped.
moderation	body	object	No	Configuration for running moderation on the input and output of this response.
stream	body	boolean	No	If set to true, the model response data will be streamed to the client as it is generated using [server-sent events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#Event_stream_format). See the [Streaming section below](https://developers.openai.com/api/reference/resources/chat/subresources/completions/streaming-events) for more information, along with the [streaming responses](https://developers.openai.com/api/docs/guides/streaming-responses) guide for more information on how to handle the streaming events.
stop	body	string	No	Not supported with latest reasoning models `o3` and `o4-mini`. Up to 4 sequences where the API will stop generating further tokens. The returned text will not contain the stop sequence.
logit_bias	body	object	No	Modify the likelihood of specified tokens appearing in the completion. Accepts a JSON object that maps tokens (specified by their token ID in the tokenizer) to an associated bias value from -100 to 100. Mathematically, the bias is added to the logits generated by the model prior to sampling. The exact effect will vary per model, but values between -1 and 1 should decrease or increase likelihood of selection; values like -100 or 100 should result in a ban or exclusive selection of the relevant token.
logprobs	body	boolean	No	Whether to return log probabilities of the output tokens or not. If true, returns the log probabilities of each output token returned in the `content` of `message`.
max_tokens	body	integer	No	The maximum number of [tokens](https://platform.openai.com/tokenizer) that can be generated in the chat completion. This value can be used to control [costs](https://openai.com/api/pricing/) for text generated via API. This value is now deprecated in favor of `max_completion_tokens`, and is not compatible with [o-series models](https://developers.openai.com/api/docs/guides/reasoning).
n	body	integer	No	How many chat completion choices to generate for each input message. Note that you will be charged based on the number of generated tokens across all of the choices. Keep `n` as `1` to minimize costs.
prediction	body	object	No	Configuration for a [Predicted Output](https://developers.openai.com/api/docs/guides/predicted-outputs), which can greatly improve response times when large parts of the model response are known ahead of time. This is most common when you are regenerating a file with only minor changes to most of the content.
seed	body	integer	No	This feature is in Beta. If specified, our system will make a best effort to sample deterministically, such that repeated requests with the same `seed` and parameters should return the same result. Determinism is not guaranteed, and you should refer to the `system_fingerprint` response parameter to monitor changes in the backend.
stream_options	body	object	No	Options for streaming response. Only set this when you set `stream: true`.
tools	body	object[]	No	A list of tools the model may call. You can provide either [custom tools](https://developers.openai.com/api/docs/guides/function-calling#custom-tools) or [function tools](https://developers.openai.com/api/docs/guides/function-calling).
tool_choice	body	string	No	Controls which (if any) tool is called by the model. `none` means the model will not call any tool and instead generates a message. `auto` means the model can pick between generating a message or calling one or more tools. `required` means the model must call one or more tools. Specifying a particular tool via `{"type": "function", "function": {"name": "my_function"}}` forces the model to call that tool. `none` is the default when no tools are present. `auto` is the default if tools are present.
parallel_tool_calls	body	boolean	No	Whether to enable [parallel function calling](https://developers.openai.com/api/docs/guides/function-calling#parallel-function-calling) during tool use.
function_call	body	string	No	Deprecated in favor of `tool_choice`. Controls which (if any) function is called by the model. `none` means the model will not call a function and instead generates a message. `auto` means the model can pick between generating a message or calling a function. Specifying a particular function via `{"name": "my_function"}` forces the model to call that function. `none` is the default when no functions are present. `auto` is the default if functions are present.
functions	body	object[]	No	Deprecated in favor of `tools`. A list of functions the model may generate JSON inputs for.

Response 200 OK

{
  "id": "string",
  "choices": [
    {
      "finish_reason": "stop",
      "index": 0,
      "message": {
        "content": "string",
        "refusal": "string",
        "tool_calls": [
          {
            "id": "[recursive or deeply nested schema]",
            "type": "[recursive or deeply nested schema]",
            "function": "[recursive or deeply nested schema]"
          }
        ],
        "annotations": [
          {
            "type": "[recursive or deeply nested schema]",
            "url_citation": "[recursive or deeply nested schema]"
          }
        ],
        "role": "assistant",
        "function_call": {
          "arguments": "string",
          "name": "string"
        },
        "audio": {
          "id": "string",
          "expires_at": 0,
          "data": "string",
          "transcript": "string"
        }
      },
      "logprobs": {
        "content": [
          {
            "token": "[recursive or deeply nested schema]",
            "logprob": "[recursive or deeply nested schema]",
            "bytes": "[recursive or deeply nested schema]",
            "top_logprobs": "[recursive or deeply nested schema]"
          }
        ],
        "refusal": [
          {
            "token": "[recursive or deeply nested schema]",
            "logprob": "[recursive or deeply nested schema]",
            "bytes": "[recursive or deeply nested schema]",
            "top_logprobs": "[recursive or deeply nested schema]"
          }
        ]
      }
    }
  ],
  "created": 0,
  "model": "string",
  "metadata": {},
  "service_tier": "auto",
  "system_fingerprint": "string",
  "object": "chat.completion",
  "usage": {
    "completion_tokens": 0,
    "prompt_tokens": 0,
    "total_tokens": 0,
    "completion_tokens_details": {
      "accepted_prediction_tokens": 0,
      "audio_tokens": 0,
      "reasoning_tokens": 0,
      "text_tokens": 0,
      "rejected_prediction_tokens": 0
    },
    "prompt_tokens_details": {
      "audio_tokens": 0,
      "cached_tokens": 0,
      "text_tokens": 0,
      "image_tokens": 0,
      "cache_write_tokens": 0
    }
  },
  "moderation": {
    "input": {
      "type": "moderation_results",
      "model": "string",
      "results": [
        {
          "type": "moderation_result",
          "model": "string",
          "flagged": true,
          "categories": {},
          "category_scores": {},
          "category_applied_input_types": {}
        }
      ]
    },
    "output": {
      "type": "moderation_results",
      "model": "string",
      "results": [
        {
          "type": "moderation_result",
          "model": "string",
          "flagged": true,
          "categories": {},
          "category_scores": {},
          "category_applied_input_types": {}
        }
      ]
    }
  }
}

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