> ## Documentation Index
> Fetch the complete documentation index at: https://docs.crazyrouter.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Chat Completion Object

> Core production-oriented structure of Chat Completion and Chat Completion Chunk objects

> Last updated: 2026-06-06

# Chat Completion Object

`/v1/chat/completions` returns `chat.completion` for non-streaming requests and `chat.completion.chunk` for streaming requests.

This page focuses on the most stable, broadly useful OpenAI-compatible response structure on Crazyrouter today.

## Non-streaming object

Minimal production request:

```bash cURL theme={null}
curl https://api.crazyrouter.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gpt-5.5",
    "messages": [
      {
        "role": "user",
        "content": "Explain what a REST API is in one sentence."
      }
    ],
    "max_tokens": 64
  }'
```

Typical production response skeleton:

```json theme={null}
{
  "id": "chatcmpl-xxx",
  "object": "chat.completion",
  "created": 1774177466,
  "model": "gpt-5.5",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "...",
        "reasoning_content": null,
        "tool_calls": null
      },
      "finish_reason": "stop"
    }
  ]
}
```

### How to read it

* `message.content` is the final text answer
* `message.tool_calls` only appears when the model is requesting tool execution
* `message.reasoning_content` may appear for some models or routes, but should not currently be treated as a guaranteed field

***

## Streaming object

For streaming requests, the server returns `chat.completion.chunk` SSE events:

```json theme={null}
{
  "id": "chatcmpl-xxx",
  "object": "chat.completion.chunk",
  "created": 1774177466,
  "model": "gpt-5.5",
  "choices": [
    {
      "index": 0,
      "delta": {
        "role": "assistant",
        "content": "..."
      },
      "finish_reason": null
    }
  ]
}
```

Common SSE shape:

```text theme={null}
data: {"object":"chat.completion.chunk",...}
data: {"choices":[{"delta":{"content":"..."}}],...}
data: [DONE]
```

***

## Fields you will usually care about

| Field                          | Meaning                                                                    |
| ------------------------------ | -------------------------------------------------------------------------- |
| `object`                       | `chat.completion` for non-streaming, `chat.completion.chunk` for streaming |
| `model`                        | The actual model used for the response                                     |
| `choices[].message.content`    | Final non-streaming text                                                   |
| `choices[].message.tool_calls` | Non-streaming tool requests                                                |
| `choices[].delta.content`      | Streaming text delta                                                       |
| `choices[].finish_reason`      | Stop reason such as `stop`, `length`, or `tool_calls`                      |

<Note>
  Upstream models may pass through extra fields. Client code should rely on the stable common fields first rather than assuming every model exposes the same extensions.
</Note>