> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt.

# Post Chat Completion

POST https://fai.buildwithfern.com/chat/{domain}
Content-Type: application/json

Reference: https://buildwithfern.com/learn/docs/scribe-api/chat/post-chat-completion

## Authentication

- `Authorization` header (bearer token, required) — Bearer authentication of the form `Bearer <token>`, where token is your auth token.

## Servers

- `https://fai.buildwithfern.com` (Production, default)
- `https://fai-dev.buildwithfern.com` (Development)
- `http://localhost:8080` (Local)

## Request

### Path parameters

- `domain` (string, required)

### Body (application/json)

This endpoint expects an object.

- `messages` (list of object, required) — The messages to use for the chat completion
  - `role` (enum, required)
    - Allowed values: `user`, `assistant`
  - `content` (string, required)
- `model` (enum, optional, nullable) — The model to use for the chat completion
  - Allowed values: `claude-4-sonnet`, `claude-4.5-haiku`, `claude-4.5-sonnet`, `claude-4.6-sonnet`
- `max_tokens` (integer, optional, nullable, default: 3000) — The maximum number of tokens to generate. Note: setting a token count lower than 2000 may result in incomplete responses. You can add a custom system prompt to control the verbosity of the response.
- `system_prompt` (string, optional, nullable) — The system prompt to use for the chat completion
- `rewrite_query` (boolean, optional, nullable, default: false) — Whether to rewrite the query using query decomposition

## Response

### 200

Successful Response

- `turns` (list of object, required) — The conversation turns in the chat completion
  - `role` (enum, required)
    - Allowed values: `user`, `assistant`
  - `content` (string, required)
- `citations` (list of string, required) — List of citation strings

## Errors

### 422 Unprocessable Entity Error

Validation Error

- `detail` (list of object, optional)
  - `loc` (list of string or integer, required)
  - `msg` (string, required)
  - `type` (string, required)

## Examples

**Request**

```json
{
  "messages": [
    {
      "role": "user",
      "content": "string"
    }
  ]
}
```

**Response**

```json
{
  "turns": [
    {
      "role": "user",
      "content": "string"
    }
  ],
  "citations": [
    "string"
  ]
}
```