# Structured outputs

Get JSON from the model with response_format, with or without a JSON Schema.

## JSON that matches a schema

`response_format` of type `json_schema` asks the model for JSON that follows your schema. The router sends such a request only to routes that support structured output (the **Structured output** capability in the [catalog](/models)); a model without one is a `400` "no route".

```json
{
  "model": "openai/gpt-4o-mini",
  "messages": [{ "role": "user", "content": "Extract the city and the date: meet me in Kazan on 3 May." }],
  "response_format": {
    "type": "json_schema",
    "json_schema": {
      "name": "meeting",
      "strict": true,
      "schema": {
        "type": "object",
        "properties": { "city": { "type": "string" }, "date": { "type": "string" } },
        "required": ["city", "date"],
        "additionalProperties": false
      }
    }
  }
}
```

The answer's `message.content` is a JSON string: parse it.

## Any valid JSON

`{"type": "json_object"}` asks for valid JSON without a schema. The router does not check that the model supports it: say in the prompt that you want JSON, and handle a parsing error.

## Tips

- Keep the schema small: it is billed as input tokens.
- Even with `strict`, check the result in your code; an answer cut by `max_tokens` (`finish_reason: "length"`) is not valid JSON.