# Messages - Official Anthropic Format

**Method**: `POST`
**Endpoint**: `/v1/messages`

This endpoint calls available Claude / LLM models with the Anthropic Messages format. The full request URL is `{BaseURL}/v1/messages`. For Base URL and API key setup, see [Get Base URL and API Key](/en/api/doc-6535931).

## Minimal Text Request

## Request Parameters

### Header Parameters

```text
Authorization
string
Required
Default Value:
Bearer YOUR_API_KEY
```

```text
Content-Type
string
Required
Default Value:
application/json
```

```text
anthropic-version
string
Optional
Example:
2023-06-01
```

### Body Parameters application/json

```text
object
Example
{
  "model": "claude-3-5-sonnet-20240620",
  "max_tokens": 1024,
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "type": "text",
          "text": "Hello, Claude format."
        }
      ]
    }
  ]
}
```

Common fields:

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `model` | string | Yes | Model name. Check available models with [List Models](/en/api/api-287780941). |
| `max_tokens` | number | Yes | Maximum output tokens. |
| `messages` | array | Yes | Message array in Anthropic Messages format. |
| `messages[].role` | string | Yes | Usually `user` or `assistant`. |
| `messages[].content` | array | Yes | Content block array. Text blocks use `{ "type": "text", "text": "..." }`. |
| `stream` | boolean | No | Whether to use streaming, depending on upstream model support. |

## Example Request

### Shell

```bash
curl --location --request POST '{BaseURL}/v1/messages' \
--header 'Authorization: Bearer YOUR_API_KEY' \
--header 'Content-Type: application/json' \
--data-raw '{
  "model": "claude-3-5-sonnet-20240620",
  "max_tokens": 1024,
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "type": "text",
          "text": "Hello, Claude format."
        }
      ]
    }
  ]
}'
```

## Image Requests

Image understanding uses the same `/v1/messages` endpoint. Add an `image` content block to `content`. See [Messages - Vision](/en/api/api-266125082) for an image payload example.

## Migration Notes

- If you previously called the official Anthropic API, you usually only need to replace the Base URL and API key, then confirm that the `model` name is available to your account.
- If you previously called OpenAI Chat Completions, change the endpoint from `/v1/chat/completions` to `/v1/messages` and convert message content into Anthropic content blocks.
- Do not expose API keys in public frontend code, logs, screenshots, or GitHub.

## Response

### 🟢 200 Success

**Content Type**: `application/json`

#### Response Schema

```text
object
```

#### Example

```json
{
  "id": "msg_xxx",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "Hello. How can I help?"
    }
  ],
  "model": "claude-3-5-sonnet-20240620",
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 12,
    "output_tokens": 8
  }
}
```