# Structured Outputs

> Constrain responses to JSON or a JSON Schema with response_format.

Use `response_format` to get machine-readable output.

## JSON Schema

```python
schema = {
    "type": "object",
    "properties": {
        "name": {"type": "string"},
        "context_tokens": {"type": "integer"},
    },
    "required": ["name", "context_tokens"],
    "additionalProperties": False,
}

completion = client.chat.completions.create(
    model="Qwen/Qwen3.8-27B",
    messages=[{"role": "user", "content": "Describe DeepSeek V4 Flash."}],
    response_format={"type": "json_schema", "json_schema": {"name": "model_card", "schema": schema, "strict": True}},
)
```

## JSON mode

`{"type": "json_object"}` asks for valid JSON without a schema. Tell the model in your prompt what shape you expect.

## Notes

- Support varies by model — look for **Structured outputs** in [Models](/docs/getting-started/models).
- Always parse and validate the result; if generation hits `max_tokens`, the JSON can be truncated
  (`finish_reason: "length"`).