Merge pull request #33 from csells/required-fields-fix

Preserve required fields in ToolInputSchema

Author: leehack

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.2
+
+- Preserve required fields in ToolInputSchema
+
 ## 0.5.1
 
 - Add support for OutputScheme (<https://modelcontextprotocol.io/specification/draft/server/tools#output-schema>)

example/iostream-client-server/simple.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:mcp_dart/mcp_dart.dart';
 import 'server_iostream.dart';
+
 /// Creates and returns a client with custom stream transport connected to a server.
 Future<void> main() async {
   // Create a client
@@ -15,7 +16,7 @@ Future<void> main() async {
   // Create custom streams for transport
   final serverToClientStreamController = StreamController<List<int>>();
   final clientToServerStreamController = StreamController<List<int>>();
-  
+
   // Create transport using custom streams
   final clientTransport = IOStreamTransport(
     stream: serverToClientStreamController.stream,

example/required_fields_demo.dart

@@ -0,0 +1,114 @@
+import 'package:mcp_dart/mcp_dart.dart';
+
+void main() {
+  // Create a tool with required fields - this simulates what an MCP server would send
+  final calculatorTool = Tool(
+    name: 'calculate',
+    description: 'Performs mathematical calculations',
+    inputSchema: ToolInputSchema(
+      properties: {
+        'operation': {
+          'type': 'string',
+          'enum': ['add', 'subtract', 'multiply', 'divide'],
+          'description': 'The mathematical operation to perform'
+        },
+        'a': {'type': 'number', 'description': 'First number'},
+        'b': {'type': 'number', 'description': 'Second number'},
+        'precision': {
+          'type': 'integer',
+          'description': 'Number of decimal places (optional)',
+          'default': 2
+        }
+      },
+      required: ['operation', 'a', 'b'], // ← This is now preserved!
+    ),
+    outputSchema: ToolOutputSchema(
+      properties: {
+        'result': {'type': 'number', 'description': 'The calculation result'},
+        'equation': {
+          'type': 'string',
+          'description': 'The equation that was calculated'
+        }
+      },
+      required: ['result'], // ← Output required fields also preserved!
+    ),
+  );
+
+  print('=== MCP Tool Schema Demo ===');
+  print('Tool: ${calculatorTool.name}');
+  print('Description: ${calculatorTool.description}');
+
+  // Serialize to JSON (what MCP client receives)
+  final toolJson = calculatorTool.toJson();
+  print('\n=== Serialized Tool JSON ===');
+  print('Input required fields: ${toolJson['inputSchema']['required']}');
+  print('Output required fields: ${toolJson['outputSchema']['required']}');
+
+  // This demonstrates the fix - required fields are preserved in JSON
+  print('\n=== Full Input Schema ===');
+  final inputSchema = toolJson['inputSchema'] as Map<String, dynamic>;
+  print('Type: ${inputSchema['type']}');
+  print('Required: ${inputSchema['required']}');
+  print('Properties: ${(inputSchema['properties'] as Map).keys.join(', ')}');
+
+  // Deserialize back from JSON (roundtrip test)
+  final deserializedTool = Tool.fromJson(toolJson);
+  print('\n=== Roundtrip Test ===');
+  print('Original required: ${calculatorTool.inputSchema.required}');
+  print('Deserialized required: ${deserializedTool.inputSchema.required}');
+  print(
+      'Match: ${_listsEqual(calculatorTool.inputSchema.required, deserializedTool.inputSchema.required)}');
+
+  // Convert to OpenAI function calling format
+  print('\n=== OpenAI Function Format ===');
+  final openaiFunction = <String, dynamic>{
+    'type': 'function',
+    'function': <String, dynamic>{
+      'name': calculatorTool.name,
+      'description': calculatorTool.description,
+      'parameters': calculatorTool.inputSchema.toJson(),
+    }
+  };
+
+  final functionObj = openaiFunction['function'] as Map<String, dynamic>;
+  final parameters = functionObj['parameters'] as Map<String, dynamic>;
+  print('Function name: ${functionObj['name']}');
+  print('Required parameters: ${parameters['required']}');
+  print('✓ Ready for LLM integration!');
+
+  // Convert to Anthropic Claude format
+  print('\n=== Anthropic Claude Format ===');
+  final anthropicTool = <String, dynamic>{
+    'name': calculatorTool.name,
+    'description': calculatorTool.description,
+    'input_schema': calculatorTool.inputSchema.toJson(),
+  };
+
+  final claudeSchema = anthropicTool['input_schema'] as Map<String, dynamic>;
+  print('Tool name: ${anthropicTool['name']}');
+  print('Required parameters: ${claudeSchema['required']}');
+  print('✓ Ready for Claude integration!');
+
+  // Simulate a real MCP server response
+  print('\n=== Simulated MCP Server Response ===');
+  final listToolsResult = ListToolsResult(tools: [calculatorTool]);
+  final serverResponse = listToolsResult.toJson();
+
+  print('Server response preserves required fields:');
+  final tools = serverResponse['tools'] as List;
+  final firstTool = tools[0] as Map<String, dynamic>;
+  final firstToolInputSchema = firstTool['inputSchema'] as Map<String, dynamic>;
+  print('  Tool: ${firstTool['name']}');
+  print('  Required: ${firstToolInputSchema['required']}');
+  print('✓ MCP server integration works!');
+}
+
+bool _listsEqual(List<String>? a, List<String>? b) {
+  if (a == null && b == null) return true;
+  if (a == null || b == null) return false;
+  if (a.length != b.length) return false;
+  for (int i = 0; i < a.length; i++) {
+    if (a[i] != b[i]) return false;
+  }
+  return true;
+}

lib/src/types.dart

@@ -1626,19 +1626,25 @@ class ToolInputSchema {
   /// JSON Schema properties definition.
   final Map<String, dynamic>? properties;
 
+  /// List of required property names.
+  final List<String>? required;
+
   const ToolInputSchema({
     this.properties,
+    this.required,
   });
 
   factory ToolInputSchema.fromJson(Map<String, dynamic> json) {
     return ToolInputSchema(
       properties: json['properties'] as Map<String, dynamic>?,
+      required: (json['required'] as List<dynamic>?)?.cast<String>(),
     );
   }
 
   Map<String, dynamic> toJson() => {
         'type': type,
         if (properties != null) 'properties': properties,
+        if (required != null && required!.isNotEmpty) 'required': required,
       };
 }
 
@@ -1650,19 +1656,25 @@ class ToolOutputSchema {
   /// JSON Schema properties definition.
   final Map<String, dynamic>? properties;
 
+  /// List of required property names.
+  final List<String>? required;
+
   const ToolOutputSchema({
     this.properties,
+    this.required,
   });
 
   factory ToolOutputSchema.fromJson(Map<String, dynamic> json) {
     return ToolOutputSchema(
       properties: json['properties'] as Map<String, dynamic>?,
+      required: (json['required'] as List<dynamic>?)?.cast<String>(),
     );
   }
 
   Map<String, dynamic> toJson() => {
         'type': type,
         if (properties != null) 'properties': properties,
+        if (required != null && required!.isNotEmpty) 'required': required,
       };
 }
 

pubspec.yaml

@@ -1,6 +1,6 @@
 name: mcp_dart
 description: Dart Implementation of Model Context Protocol (MCP) SDK.
-version: 0.5.1
+version: 0.5.2
 repository: https://github.com/leehack/mcp_dart
 
 environment: