Use shared Implementation type, add clientInfo field to MCPServer (#175)

In the [latest schema](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/2025-03-26/schema.json) the ClientImplementation and ServerImplementation types were merged into a single Implementation type, this updates things to match.

Also closes #173 which will make #174 slightly cleaner, and matches what we do for ServerConnection as well.

Author: jakemac53

mcp_examples/bin/file_system_server.dart

@@ -33,10 +33,7 @@ final class SimpleFileSystemServer extends MCPServer
     with LoggingSupport, RootsTrackingSupport, ToolsSupport {
   SimpleFileSystemServer.fromStreamChannel(super.channel)
     : super.fromStreamChannel(
-        implementation: ServerImplementation(
-          name: 'file system',
-          version: '0.0.1',
-        ),
+        implementation: Implementation(name: 'file system', version: '0.0.1'),
       );
 
   @override

mcp_examples/bin/workflow_client.dart

@@ -107,9 +107,7 @@ final class WorkflowClient extends MCPClient with RootsSupport {
        stdinQueue = StreamQueue(
          stdin.transform(utf8.decoder).transform(const LineSplitter()),
        ),
-       super(
-         ClientImplementation(name: 'Gemini workflow client', version: '0.1.0'),
-       ) {
+       super(Implementation(name: 'Gemini workflow client', version: '0.1.0')) {
     logSink = _createLogSink(logFile);
     addRoot(
       Root(

mcp_examples/pubspec.yaml

@@ -14,3 +14,7 @@ dependencies:
   google_generative_ai: ^0.4.7
   path: ^1.9.1
   stream_channel: ^2.1.4
+
+dependency_overrides:
+  dart_mcp:
+    path: ../pkgs/dart_mcp

pkgs/dart_mcp/CHANGELOG.md

@@ -1,5 +1,9 @@
-## 0.2.2-wip
+## 0.2.2
 
+- Refactor `ClientImplementation` and `ServerImplementation` to the shared
+  `Implementation` type to match the spec. The old names are deprecated but will
+  still work until the next breaking release.
+- Add `clientInfo` field to `MCPServer`, assigned during initialization.
 - Move the `done` future from the `ServerConnection` into `MCPBase` so it is
   available to the `MPCServer` class as well.
 

pkgs/dart_mcp/README.md

@@ -36,7 +36,7 @@ an error, which may result in a better UX for the users of the client.
 
 To implement a client, import `package:dart_mcp/client.dart` and extend the
 `MCPClient` class, or directly call its constructor with a
-`ClientImplementation` if you aren't implementing any "capabilities".
+`Implementation` if you aren't implementing any "capabilities".
 
 For each specific MCP capability your client supports, there is a corresponding
 mixin that you can use (`RootsSupport`, `SamplingSupport`, etc). Each mixin has

pkgs/dart_mcp/example/simple_client.dart

@@ -6,7 +6,7 @@ import 'package:dart_mcp/client.dart';
 
 void main() async {
   final client = MCPClient(
-    ClientImplementation(name: 'example dart client', version: '0.1.0'),
+    Implementation(name: 'example dart client', version: '0.1.0'),
   );
   print('connecting to server');
   final server = await client.connectStdioServer('dart', [

pkgs/dart_mcp/example/simple_server.dart

@@ -29,7 +29,7 @@ void main() {
 base class DartMCPServer extends MCPServer with ToolsSupport {
   DartMCPServer(super.channel)
     : super.fromStreamChannel(
-        implementation: ServerImplementation(
+        implementation: Implementation(
           name: 'example dart server',
           version: '0.1.0',
         ),

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

@@ -13,7 +13,7 @@ extension type InitializeRequest._fromMap(Map<String, Object?> _value)
   factory InitializeRequest({
     required ProtocolVersion protocolVersion,
     required ClientCapabilities capabilities,
-    required ClientImplementation clientInfo,
+    required Implementation clientInfo,
     MetaWithProgressToken? meta,
   }) => InitializeRequest._fromMap({
     'protocolVersion': protocolVersion.versionString,
@@ -33,8 +33,7 @@ extension type InitializeRequest._fromMap(Map<String, Object?> _value)
   ClientCapabilities get capabilities =>
       _value['capabilities'] as ClientCapabilities;
 
-  ClientImplementation get clientInfo =>
-      _value['clientInfo'] as ClientImplementation;
+  Implementation get clientInfo => _value['clientInfo'] as Implementation;
 }
 
 /// After receiving an initialize request from the client, the server sends
@@ -44,7 +43,7 @@ extension type InitializeResult.fromMap(Map<String, Object?> _value)
   factory InitializeResult({
     required ProtocolVersion protocolVersion,
     required ServerCapabilities serverCapabilities,
-    required ServerImplementation serverInfo,
+    required Implementation serverInfo,
     String? instructions,
   }) => InitializeResult.fromMap({
     'protocolVersion': protocolVersion.versionString,
@@ -74,8 +73,7 @@ extension type InitializeResult.fromMap(Map<String, Object?> _value)
   ServerCapabilities get capabilities =>
       _value['capabilities'] as ServerCapabilities;
 
-  ServerImplementation get serverInfo =>
-      _value['serverInfo'] as ServerImplementation;
+  Implementation get serverInfo => _value['serverInfo'] as Implementation;
 
   /// Instructions describing how to use the server and its features.
   ///
@@ -295,24 +293,17 @@ extension type Tools.fromMap(Map<String, Object?> _value) {
   }
 }
 
-/// Describes the name and version of an MCP client implementation.
-extension type ClientImplementation.fromMap(Map<String, Object?> _value) {
-  factory ClientImplementation({
-    required String name,
-    required String version,
-  }) => ClientImplementation.fromMap({'name': name, 'version': version});
+/// Describes the name and version of an MCP implementation.
+extension type Implementation.fromMap(Map<String, Object?> _value) {
+  factory Implementation({required String name, required String version}) =>
+      Implementation.fromMap({'name': name, 'version': version});
 
   String get name => _value['name'] as String;
   String get version => _value['version'] as String;
 }
 
-/// Describes the name and version of an MCP server implementation.
-extension type ServerImplementation.fromMap(Map<String, Object?> _value) {
-  factory ServerImplementation({
-    required String name,
-    required String version,
-  }) => ServerImplementation.fromMap({'name': name, 'version': version});
+@Deprecated('Use Implementation instead.')
+typedef ClientImplementation = Implementation;
 
-  String get name => _value['name'] as String;
-  String get version => _value['version'] as String;
-}
+@Deprecated('Use Implementation instead.')
+typedef ServerImplementation = Implementation;

pkgs/dart_mcp/lib/src/client/client.dart

@@ -29,7 +29,7 @@ part 'sampling_support.dart';
 /// this will be invoked at the end of base class constructor.
 base class MCPClient {
   /// A description of the client sent to servers during initialization.
-  final ClientImplementation implementation;
+  final Implementation implementation;
 
   MCPClient(this.implementation) {
     initialize();
@@ -128,10 +128,10 @@ base class ServerConnection extends MCPBase {
   /// protocol version.
   late ProtocolVersion protocolVersion;
 
-  /// The [ServerImplementation] returned from the [initialize] request.
+  /// The [Implementation] returned from the [initialize] request.
   ///
   /// Only non-null after [initialize] has successfully completed.
-  ServerImplementation? serverInfo;
+  Implementation? serverInfo;
 
   /// The [ServerCapabilities] returned from the [initialize] request.
   ///

pkgs/dart_mcp/lib/src/client/sampling_support.dart

@@ -26,6 +26,6 @@ base mixin SamplingSupport on MCPClient {
   /// request gave when it was initialized.
   FutureOr<CreateMessageResult> handleCreateMessage(
     CreateMessageRequest request,
-    ServerImplementation serverInfo,
+    Implementation serverInfo,
   );
 }