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POST

POST /assistants/{assistant_id} — OpenAI API

Deprecated

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

OpenAI API

Modify assistant

Base URL
https://api.openai.com/v1
Auth
Authorization: Bearer <OPENAI_API_KEY>
Last verified
2026-10-20 · upstream hash matched
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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/assistants/assistant-id' \  -H "Authorization: Bearer $OPENAI_API_KEY" \  -H 'Content-Type: application/json' \  -d '{}'

Parameters

Name In Type Required Description
assistant_id path string Yes The ID of the assistant to modify.
model body string No ID of the model to use. You can use the [List models](https://developers.openai.com/api/reference/resources/models/methods/list) API to see all of your available models, or see our [Model overview](https://developers.openai.com/api/docs/models) for descriptions of them.
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.
name body string No The name of the assistant. The maximum length is 256 characters.
description body string No The description of the assistant. The maximum length is 512 characters.
instructions body string No The system instructions that the assistant uses. The maximum length is 256,000 characters.
tools body object[] No A list of tool enabled on the assistant. There can be a maximum of 128 tools per assistant. Tools can be of types `code_interpreter`, `file_search`, or `function`.
tool_resources body object No A set of resources that are used by the assistant's tools. The resources are specific to the type of tool. For example, the `code_interpreter` tool requires a list of file IDs, while the `file_search` tool requires a list of vector store IDs.
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.
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.
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.
response_format body string No Specifies the format that the model must output. Compatible with [GPT-4o](https://developers.openai.com/api/docs/models/gpt-4o), [GPT-4 Turbo](https://developers.openai.com/api/docs/models/gpt-4-turbo), and all GPT-3.5 Turbo models since `gpt-3.5-turbo-1106`. 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 JSON mode, which ensures the message the model generates is valid JSON. **Important:** when using JSON mode, you **must** also instruct the model to produce JSON yourself via a system or user message. Without this, the model may generate an unending stream of whitespace until the generation reaches the token limit, resulting in a long-running and seemingly "stuck" request. Also note that the message content may be partially cut off if `finish_reason="length"`, which indicates the generation exceeded `max_tokens` or the conversation exceeded the max context length.

Response 200 OK

{
  "id": "string",
  "object": "assistant",
  "created_at": 0,
  "name": "string",
  "description": "string",
  "model": "string",
  "instructions": "string",
  "tools": [],
  "tool_resources": {
    "code_interpreter": {
      "file_ids": []
    },
    "file_search": {
      "vector_store_ids": [
        "string"
      ]
    }
  },
  "metadata": {},
  "temperature": 1,
  "top_p": 1,
  "response_format": "auto"
}
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