migrate dart_mcp to package:checks

.gitignore

@@ -5,6 +5,7 @@ pubspec.lock
 .vscode
 .idea
 *.iml
+.agents
 
 # Gemini specific ignores
 **/.gemini/*

pkgs/dart_mcp/lib/api.dart

@@ -0,0 +1,5 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+export 'src/api/api.dart';

pkgs/dart_mcp/lib/client.dart

@@ -2,5 +2,5 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-export 'src/api/api.dart';
+export 'api.dart';
 export 'src/client/client.dart';

pkgs/dart_mcp/lib/server.dart

@@ -2,5 +2,5 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-export 'src/api/api.dart';
+export 'api.dart';
 export 'src/server/server.dart';

pkgs/dart_mcp/lib/src/api/api.dart

@@ -61,10 +61,10 @@ enum ProtocolVersion {
 
 /// A progress token, used to associate progress notifications with the original
 /// request.
-extension type ProgressToken(/*String|int*/ Object _) {}
+extension type ProgressToken(/*String|int*/ Object _) implements Object {}
 
 /// An opaque token used to represent a cursor for pagination.
-extension type Cursor(String _) {}
+extension type Cursor(String _) implements Object {}
 
 /// Generic metadata passed with most requests.
 ///
@@ -92,15 +92,16 @@ extension type Cursor(String _) {}
 /// - Name: Unless empty, MUST begin and end with an alphanumeric character
 ///   (`[a-z0-9A-Z]`). MAY contain hyphens (`-`), underscores (`_`), dots
 ///   (`.`), and alphanumerics in between.
-extension type Meta.fromMap(Map<String, Object?> _value) {
+extension type Meta.fromMap(Map<String, Object?> _value) implements Object {
   Object? operator [](String key) => _value[key];
 }
 
 /// Basic metadata required by multiple types.
 ///
 /// Not to be confused with the `_meta` property in the spec, which has a
 /// different purpose.
-extension type BaseMetadata.fromMap(Map<String, Object?> _value) {
+extension type BaseMetadata.fromMap(Map<String, Object?> _value)
+    implements Object {
   factory BaseMetadata({required String name, String? title}) =>
       BaseMetadata.fromMap({Keys.name: name, Keys.title: title});
 
@@ -130,7 +131,8 @@ extension type BaseMetadata.fromMap(Map<String, Object?> _value) {
 /// [ProgressToken] at the key "progressToken".
 ///
 /// Should be "mixed in" by implementing this type from other extension types.
-extension type WithProgressToken.fromMap(Map<String, Object?> _value) {
+extension type WithProgressToken.fromMap(Map<String, Object?> _value)
+    implements Object {
   ProgressToken? get progressToken =>
       _value[Keys.progressToken] as ProgressToken?;
 }
@@ -147,7 +149,8 @@ extension type MetaWithProgressToken.fromMap(Map<String, Object?> _value)
 /// Base interface for all types that can have arbitrary metadata attached.
 ///
 /// Should not be constructed directly, and has no public constructor.
-extension type WithMetadata._fromMap(Map<String, Object?> _value) {
+extension type WithMetadata._fromMap(Map<String, Object?> _value)
+    implements Object {
   /// The `_meta` property/parameter is reserved by MCP to allow clients and
   /// servers to attach additional metadata to their interactions.
   ///
@@ -171,14 +174,14 @@ extension type Request._fromMap(Map<String, Object?> _value)
 }
 
 /// Base interface for all notifications.
-extension type Notification(Map<String, Object?> _value) {
+extension type Notification(Map<String, Object?> _value) implements Object {
   /// This parameter name is reserved by MCP to allow clients and servers to
   /// attach additional metadata to their notifications.
   Meta? get meta => _value[Keys.meta] as Meta?;
 }
 
 /// Base interface for all responses to requests.
-extension type Result._(Map<String, Object?> _value) {
+extension type Result._(Map<String, Object?> _value) implements Object {
   Meta? get meta => _value[Keys.meta] as Meta?;
 }
 
@@ -226,7 +229,7 @@ extension type CancelledNotification.fromMap(Map<String, Object?> _value)
 }
 
 /// An opaque request ID.
-extension type RequestId(/*String|int*/ Parameter _) {}
+extension type RequestId(/*String|int*/ Parameter _) implements Object {}
 
 /// A ping, issued by either the server or the client, to check that the other
 /// party is still alive.
@@ -315,7 +318,7 @@ extension type PaginatedResult._fromMap(Map<String, Object?> _value)
 ///
 /// Doing `is` checks does not work because these are just extension types, they
 /// all have the same runtime type (`Map<String, Object?>`).
-extension type Content._(Map<String, Object?> _value) {
+extension type Content._(Map<String, Object?> _value) implements Object {
   factory Content.fromMap(Map<String, Object?> value) {
     assert(value.containsKey(Keys.type));
     return Content._(value);
@@ -538,13 +541,15 @@ extension type ResourceLink.fromMap(Map<String, Object?> _value)
 /// Base type for objects that include optional annotations for the client.
 ///
 /// The client can use annotations to inform how objects are used or displayed.
-extension type Annotated._fromMap(Map<String, Object?> _value) {
+extension type Annotated._fromMap(Map<String, Object?> _value)
+    implements Object {
   /// Annotations for this object.
   Annotations? get annotations => _value[Keys.annotations] as Annotations?;
 }
 
 /// The annotations for an [Annotated] object.
-extension type Annotations.fromMap(Map<String, Object?> _value) {
+extension type Annotations.fromMap(Map<String, Object?> _value)
+    implements Object {
   factory Annotations({
     List<Role>? audience,
     DateTime? lastModified,

pkgs/dart_mcp/lib/src/api/sampling.dart

@@ -138,7 +138,8 @@ extension type CreateMessageResult.fromMap(Map<String, Object?> _value)
 }
 
 /// Describes a message issued to or received from an LLM API.
-extension type SamplingMessage.fromMap(Map<String, Object?> _value) {
+extension type SamplingMessage.fromMap(Map<String, Object?> _value)
+    implements Object {
   factory SamplingMessage({required Role role, required Content content}) =>
       SamplingMessage.fromMap({Keys.role: role.name, Keys.content: content});
 

pkgs/dart_mcp/pubspec.yaml

@@ -16,5 +16,6 @@ dependencies:
   stream_transform: ^2.1.1
 
 dev_dependencies:
+  checks: ^0.3.1
   dart_flutter_team_lints: ^3.2.1
   test: ^1.25.15

pkgs/dart_mcp/test/api/api_test.dart

@@ -2,126 +2,107 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:checks/checks.dart';
 import 'package:dart_mcp/client.dart';
 import 'package:test/test.dart';
 
 void main() {
   test('protocol versions can be compared', () {
-    expect(
+    check(
       ProtocolVersion.latestSupported > ProtocolVersion.oldestSupported,
-      true,
-    );
-    expect(
+    ).isTrue();
+    check(
       ProtocolVersion.latestSupported >= ProtocolVersion.oldestSupported,
-      true,
-    );
-    expect(
+    ).isTrue();
+    check(
       ProtocolVersion.latestSupported < ProtocolVersion.oldestSupported,
-      false,
-    );
-    expect(
+    ).isFalse();
+    check(
       ProtocolVersion.latestSupported <= ProtocolVersion.oldestSupported,
-      false,
-    );
+    ).isFalse();
 
-    expect(
+    check(
       ProtocolVersion.oldestSupported > ProtocolVersion.latestSupported,
-      false,
-    );
-    expect(
+    ).isFalse();
+    check(
       ProtocolVersion.oldestSupported >= ProtocolVersion.latestSupported,
-      false,
-    );
-    expect(
+    ).isFalse();
+    check(
       ProtocolVersion.oldestSupported < ProtocolVersion.latestSupported,
-      true,
-    );
-    expect(
+    ).isTrue();
+    check(
       ProtocolVersion.oldestSupported <= ProtocolVersion.latestSupported,
-      true,
-    );
+    ).isTrue();
 
-    expect(
+    check(
       ProtocolVersion.latestSupported <= ProtocolVersion.latestSupported,
-      true,
-    );
-    expect(
+    ).isTrue();
+    check(
       ProtocolVersion.latestSupported >= ProtocolVersion.latestSupported,
-      true,
-    );
-    expect(
+    ).isTrue();
+    check(
       ProtocolVersion.latestSupported < ProtocolVersion.latestSupported,
-      false,
-    );
-    expect(
+    ).isFalse();
+    check(
       ProtocolVersion.latestSupported > ProtocolVersion.latestSupported,
-      false,
-    );
+    ).isFalse();
   });
 
   group('API object validation', () {
     test('throws when required fields are missing', () {
-      expect(() => Root.fromMap({}).uri, throwsA(isA<ArgumentError>()));
-      expect(
+      check(() => Root.fromMap({}).uri).throws<ArgumentError>();
+      check(
         () => Implementation.fromMap({'name': 'test'}).version,
-        throwsA(isA<ArgumentError>()),
-      );
-      expect(
-        () => BaseMetadata.fromMap({}).name,
-        throwsA(isA<ArgumentError>()),
-      );
+      ).throws<ArgumentError>();
+      check(() => BaseMetadata.fromMap({}).name).throws<ArgumentError>();
 
       final empty = <String, Object?>{};
 
       // Initialization
-      expect(
+      check(
         () => (empty as InitializeRequest).capabilities,
-        throwsArgumentError,
-      );
-      expect(
+      ).throws<ArgumentError>();
+      check(
         () => (empty as InitializeRequest).clientInfo,
-        throwsArgumentError,
-      );
+      ).throws<ArgumentError>();
 
       // Tools
-      expect(() => (empty as CallToolRequest).name, throwsArgumentError);
+      check(() => (empty as CallToolRequest).name).throws<ArgumentError>();
 
       // Resources
-      expect(() => (empty as ReadResourceRequest).uri, throwsArgumentError);
-      expect(() => (empty as SubscribeRequest).uri, throwsArgumentError);
-      expect(() => (empty as UnsubscribeRequest).uri, throwsArgumentError);
+      check(() => (empty as ReadResourceRequest).uri).throws<ArgumentError>();
+      check(() => (empty as SubscribeRequest).uri).throws<ArgumentError>();
+      check(() => (empty as UnsubscribeRequest).uri).throws<ArgumentError>();
 
       // Roots
-      expect(() => (empty as ListRootsResult).roots, throwsArgumentError);
+      check(() => (empty as ListRootsResult).roots).throws<ArgumentError>();
 
       // Prompts
-      expect(() => (empty as GetPromptRequest).name, throwsArgumentError);
+      check(() => (empty as GetPromptRequest).name).throws<ArgumentError>();
 
       // Completions
-      expect(() => (empty as CompleteRequest).ref, throwsArgumentError);
-      expect(() => (empty as CompleteRequest).argument, throwsArgumentError);
+      check(() => (empty as CompleteRequest).ref).throws<ArgumentError>();
+      check(() => (empty as CompleteRequest).argument).throws<ArgumentError>();
 
       // Logging
-      expect(() => (empty as SetLevelRequest).level, throwsArgumentError);
+      check(() => (empty as SetLevelRequest).level).throws<ArgumentError>();
 
       // Sampling
-      expect(
+      check(
         () => (empty as CreateMessageRequest).messages,
-        throwsArgumentError,
-      );
-      expect(
+      ).throws<ArgumentError>();
+      check(
         () => (empty as CreateMessageRequest).maxTokens,
-        throwsArgumentError,
-      );
+      ).throws<ArgumentError>();
     });
     test('meta field is parsed correctly', () {
       final root = Root.fromMap({
         'uri': 'file:///foo/bar',
         '_meta': {'foo': 'bar'},
       });
-      expect(root.meta, isNotNull);
+      check(root.meta).isNotNull();
       final metaMap = root.meta as Map;
-      expect(metaMap['foo'], 'bar');
+      check(metaMap['foo']).equals('bar');
     });
   });
 }