feat(firebaseai): auto schema generation

packages/firebase_ai/firebase_ai/example/lib/schema/generable_example.dart

@@ -0,0 +1,24 @@
+import 'package:firebase_ai/firebase_ai.dart';
+
+part 'generable_example.g.dart';
+
+@Generable(description: 'A mock user for testing')
+class MockUser {
+  @Guide(description: 'The user name', pattern: r'^[a-zA-Z]+$')
+  final String name;
+
+  @Guide(description: 'The user age', minimum: 0, maximum: 120)
+  final int age;
+
+  MockUser({required this.name, required this.age});
+
+  Map<String, dynamic> toJson() => {
+        'name': name,
+        'age': age,
+      };
+}
+
+@GenerateTool(name: 'get_mock_user')
+Future<MockUser> getMockUser(String name) async {
+  return MockUser(name: name, age: 30);
+}

packages/firebase_ai/firebase_ai/example/pubspec.yaml

@@ -37,10 +37,13 @@ dependencies:
   waveform_flutter: ^1.2.0
 
 dev_dependencies:
+  build_runner: ^2.4.8
+  firebase_ai_generator: ^0.1.0
   flutter_lints: ^4.0.0
   flutter_test:
     sdk: flutter
 
+
 flutter:
 
   # The following line ensures that the Material Icons font is

packages/firebase_ai/firebase_ai/lib/firebase_ai.dart

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+export 'src/annotations.dart' show Generable, Guide, GenerateTool;
 export 'src/api.dart'
     show
         BlockReason,
@@ -33,6 +34,7 @@ export 'src/api.dart'
         SafetyRating,
         SafetySetting,
         UsageMetadata;
+export 'src/auto_schema.dart' show AutoSchema;
 export 'src/base_model.dart'
     show
         GenerativeModel,

packages/firebase_ai/firebase_ai/lib/src/annotations.dart

@@ -0,0 +1,49 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// Annotation for classes that can be used to generate a JSON Schema.
+class Generable {
+  /// A brief description of the generated object.
+  final String? description;
+
+  /// Creates a [Generable] annotation.
+  const Generable({this.description});
+}
+
+/// Annotation for fields to provide constraints and documentation for the schema.
+class Guide {
+  /// Description of the field.
+  final String? description;
+
+  /// Minimum value for numeric fields.
+  final num? minimum;
+
+  /// Maximum value for numeric fields.
+  final num? maximum;
+
+  /// Regular expression pattern for string fields.
+  final String? pattern;
+
+  /// Creates a [Guide] annotation.
+  const Guide({this.description, this.minimum, this.maximum, this.pattern});
+}
+
+/// Annotation for functions that can be used as tools by the model.
+class GenerateTool {
+  /// The name of the tool. If omitted, the function name is used.
+  final String? name;
+
+  /// Creates a [GenerateTool] annotation.
+  const GenerateTool({this.name});
+}

packages/firebase_ai/firebase_ai/lib/src/auto_schema.dart

@@ -0,0 +1,29 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// A class that holds the JSON Schema representation and a factory to
+/// create a typed object from a JSON map.
+///
+/// This serves as a bridge between the generated schema and the SDK's
+/// type-safe methods for object generation and function calling.
+class AutoSchema<T> {
+  /// The raw JSON Schema map for the model.
+  final Map<String, dynamic> schemaMap;
+
+  /// A function that creates an instance of [T] from a JSON map.
+  final T Function(Map<String, dynamic>) fromJson;
+
+  /// Creates an [AutoSchema].
+  const AutoSchema({required this.schemaMap, required this.fromJson});
+}

packages/firebase_ai/firebase_ai/lib/src/base_model.dart

@@ -39,6 +39,7 @@ import 'live_session.dart';
 import 'platform_header_helper.dart';
 import 'server_template/template_tool.dart';
 import 'tool.dart';
+import 'auto_schema.dart';
 
 part 'generative_model.dart';
 part 'imagen/imagen_model.dart';

packages/firebase_ai/firebase_ai/lib/src/generative_model.dart

@@ -163,6 +163,54 @@ final class GenerativeModel extends BaseApiClientModel {
     return response.map(_serializationStrategy.parseGenerateContentResponse);
   }
 
+  /// Generates an object of type [T] responding to [prompt].
+  ///
+  /// Uses the provided [schema] to constrain the output to match the JSON
+  /// schema and uses [schema.fromJson] to parse the result.
+  Future<T> generateObject<T>(
+    AutoSchema<T> schema,
+    Iterable<Content> prompt, {
+    List<SafetySetting>? safetySettings,
+    GenerationConfig? generationConfig,
+    List<Tool>? tools,
+    ToolConfig? toolConfig,
+  }) async {
+    final config = GenerationConfig(
+      candidateCount: generationConfig?.candidateCount,
+      stopSequences: generationConfig?.stopSequences,
+      maxOutputTokens: generationConfig?.maxOutputTokens,
+      temperature: generationConfig?.temperature,
+      topP: generationConfig?.topP,
+      topK: generationConfig?.topK,
+      presencePenalty: generationConfig?.presencePenalty,
+      frequencyPenalty: generationConfig?.frequencyPenalty,
+      responseModalities: generationConfig?.responseModalities,
+      thinkingConfig: generationConfig?.thinkingConfig,
+      responseMimeType: 'application/json',
+      responseJsonSchema: schema.schemaMap,
+    );
+
+    final response = await generateContent(
+      prompt,
+      safetySettings: safetySettings,
+      generationConfig: config,
+      tools: tools,
+      toolConfig: toolConfig,
+    );
+
+    final text = response.text;
+    if (text == null) {
+      throw FirebaseAIException('No text returned from model');
+    }
+
+    final json = jsonDecode(text);
+    if (json is! Map<String, dynamic>) {
+      throw FirebaseAIException('Expected JSON map from model, got: $text');
+    }
+
+    return schema.fromJson(json);
+  }
+
   /// Counts the total number of tokens in [contents].
   ///
   /// Sends a "countTokens" API request for the configured model,

packages/firebase_ai/firebase_ai/test/model_test.dart

@@ -356,6 +356,55 @@ void main() {
       });
     });
 
+    group('generate object', () {
+      test('can make successful request and parse object', () async {
+        final (client, model) = createModel();
+        const prompt = 'Some prompt';
+        const result = '{"name": "John", "age": 30}';
+
+        final schema = AutoSchema<Map<String, dynamic>>(
+          schemaMap: const {
+            'type': 'OBJECT',
+            'properties': {
+              'name': {'type': 'STRING'},
+              'age': {'type': 'INTEGER'},
+            },
+          },
+          fromJson: (json) => json,
+        );
+
+        final response = await client.checkRequest(
+          () => model.generateObject(schema, [Content.text(prompt)]),
+          verifyRequest: (uri, request) {
+            expect(request['generationConfig'], {
+              'responseMimeType': 'application/json',
+              'responseJsonSchema': {
+                'type': 'OBJECT',
+                'properties': {
+                  'name': {'type': 'STRING'},
+                  'age': {'type': 'INTEGER'},
+                },
+              },
+            });
+          },
+          response: {
+            'candidates': [
+              {
+                'content': {
+                  'role': 'model',
+                  'parts': [
+                    {'text': result},
+                  ],
+                },
+              },
+            ],
+          },
+        );
+        expect(response['name'], 'John');
+        expect(response['age'], 30);
+      });
+    });
+
     group('generate content stream', () {
       test('can make successful request', () async {
         final (client, model) = createModel();

packages/firebase_ai/firebase_ai_generator/build.yaml

@@ -0,0 +1,7 @@
+builders:
+  firebase_ai_generator:
+    import: "package:firebase_ai_generator/firebase_ai_generator.dart"
+    builder_factories: ["firebaseAiBuilder"]
+    build_extensions: {".dart": [".g.dart"]}
+    auto_apply: dependents
+    build_to: source

packages/firebase_ai/firebase_ai_generator/lib/firebase_ai_generator.dart

@@ -0,0 +1,23 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:build/build.dart';
+import 'package:source_gen/source_gen.dart';
+import 'src/schema_generator.dart';
+import 'src/tool_generator.dart';
+
+/// Builder factory for Firebase AI.
+Builder firebaseAiBuilder(BuilderOptions options) {
+  return PartBuilder([SchemaGenerator(), ToolGenerator()], '.g.dart');
+}