llm_schema 0.1.0

Zod-style schema validation for LLM structured outputs. Define a schema once to validate AI-generated JSON, emit JSON Schema for tool calling, and extract JSON from messy model responses. Pure Dart, n [...]

example/llm_schema_example.dart

// ignore_for_file: avoid_print

import 'package:llm_schema/llm_schema.dart';

enum Difficulty { easy, medium, hard }

void main() {
  // Define the shape of the data you want from the model, once.
  final recipe = S.object({
    'title': S.string().nonEmpty().describe('Recipe name'),
    'servings': S.integer().min(1).describe('How many people it feeds'),
    'difficulty': S.enumOf(Difficulty.values, caseInsensitive: true),
    'ingredients': S
        .list(S.object({
          'name': S.string(),
          'quantity': S.string(),
        }))
        .nonEmpty(),
    'notes': S.string().optional(),
  });

  // 1. Ship the schema to the model as a tool / structured-output schema.
  print('--- JSON Schema for the model ---');
  print(recipe.toJsonSchemaString(pretty: true));

  // 2. Parse what the model actually sends back — fences, prose, trailing
  //    commas and all.
  const modelResponse = '''
Sure! Here's a simple recipe for you:

```json
{
  "title": "Garlic butter pasta",
  "servings": 2.0,
  "difficulty": "Easy",
  "ingredients": [
    {"name": "spaghetti", "quantity": "200 g"},
    {"name": "garlic", "quantity": "4 cloves"},
    {"name": "butter", "quantity": "50 g"},
  ],
  "extra_commentary": "Enjoy!"
}
```

Let me know if you'd like a variation.
''';

  final value = recipe.parseText(modelResponse);
  print('\n--- Parsed ---');
  print(value);
  // servings arrived as 2.0 → parsed as int 2
  // "Easy" matched Difficulty.easy (case-insensitive)
  // extra_commentary was stripped

  // 3. When the model gets it wrong, get errors you can send back to it.
  final bad = recipe.safeParseText(
    '{"title": "", "servings": 0, "difficulty": "impossible", '
    '"ingredients": []}',
  );
  if (bad case SchemaFailure(issues: _) && final failure) {
    print('\n--- Repair prompt ---');
    print(failure.toPromptString());
  }
}