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

# Llm json schema

## Overview

While working with `Inference` class, you can also generate JSON output
from the model inference. This is useful for example when you need to
process the response in a structured way or when you want to store the
elements of the response in a database.

## Example

In this example we will use OpenAI JSON Schema mode, which guarantees
that the response will be in a JSON format that matches the provided
schema.

> NOTE: Json Schema mode with guaranteed structured outputs is not
> supported by all language model providers.

```php theme={null}
<?php
require 'examples/boot.php';

use Cognesy\Messages\Messages;
use Cognesy\Polyglot\Inference\Data\ResponseFormat;
use Cognesy\Polyglot\Inference\Inference;

$data = Inference::using('openai')
    ->with(
        messages: Messages::fromString('What is capital of France? Respond with JSON data.'),
        responseFormat: ResponseFormat::jsonSchema(
            schema: [
                'type' => 'object',
                'description' => 'City information',
                'properties' => [
                    'name' => [
                        'type' => 'string',
                        'description' => 'City name',
                    ],
                    'founded' => [
                        'type' => 'integer',
                        'description' => 'Founding year',
                    ],
                    'population' => [
                        'type' => 'integer',
                        'description' => 'Current population',
                    ],
                ],
                'additionalProperties' => false,
                'required' => ['name', 'founded', 'population'],
            ],
            name: 'city_data',
            strict: true,
        ),
        options: ['max_tokens' => 64],
    )
    ->asJsonData();

echo "USER: What is capital of France\n";
echo "ASSISTANT:\n";
dump($data);

assert(is_array($data), 'Response should be an array');
assert(isset($data['name']), 'Response should have "name" field');
assert(strpos($data['name'], 'Paris') !== false, 'City name should be Paris');
assert(isset($data['population']), 'Response should have "population" field');
assert(isset($data['founded']), 'Response should have "founded" field');
?>
```