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Assistants

Create assistant

Create an assistant with a model and instructions.

post/assistants

Request body

namestring nullable

The name of the assistant. The maximum length is 256 characters.

descriptionstring nullable

The description of the assistant. The maximum length is 512 characters.

instructionsstring nullable

The system instructions that the assistant uses. The maximum length is 256,000 characters.

reasoning_effort'none' | 'minimal' | 'low' | 'medium' | 'high' | 'xhigh' | 'max' nullable

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 for model-specific support.

metadataMetadata nullable

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.

temperaturenumber nullable

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_pnumber nullable

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.

Example request

{
  "temperature": 1,
  "top_p": 1
}

Response

OK

idstring required

The identifier, which can be referenced in API endpoints.

object'assistant' required

The object type, which is always assistant.

created_atinteger required

The Unix timestamp (in seconds) for when the assistant was created.

namestring nullable required

The name of the assistant. The maximum length is 256 characters.

descriptionstring nullable required

The description of the assistant. The maximum length is 512 characters.

modelstring required

ID of the model to use. You can use the List models API to see all of your available models, or see our Model overview for descriptions of them.

instructionsstring nullable required

The system instructions that the assistant uses. The maximum length is 256,000 characters.

metadataMetadata nullable required

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.

temperaturenumber nullable

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_pnumber nullable

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.

Example response

{
  "temperature": 1,
  "top_p": 1
}

Changes

Changed in 16 of the 162 revisions of this API.43664

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    This revision also has 2 changes that name no endpoint, such as unreferenced schemas being removed. See the revision's changelog

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      response property description list-of-types was widened by adding types null to media type application/json of response 200

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      response property name list-of-types was widened by adding types null to media type application/json of response 200

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      response property tools/items/oneOf[subschema #3: Function tool]/function/strict list-of-types was widened by adding types null to media type application/json of response 200

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      response property top_p list-of-types was widened by adding types null to media type application/json of response 200

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      request property //// list-of-types was widened by adding types null to media type application/json

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    This revision also has 40 changes that name no endpoint, such as unreferenced schemas being removed. See the revision's changelog

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      added the new gpt-4.1-mini enum value to the request property ////

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      added the new gpt-4.1-mini-2025-04-14 enum value to the request property ////

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      added the new gpt-4.1-nano enum value to the request property ////

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      added the new gpt-4.1-nano-2025-04-14 enum value to the request property ////

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    This revision also has 18 changes that name no endpoint, such as unreferenced schemas being removed. See the revision's changelog

  • 6ab43fe7798e215See the full diff
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      added the new gpt-4.5-preview enum value to the request property ////

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      added the new gpt-4.5-preview-2025-02-27 enum value to the request property ////

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      added subschema #1 to the request property oneOf list

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  • 96060afbb5b912See the full diff
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