MCP(Model Context Protocol) for Dart

Model Context Protocol (MCP) is an open protocol designed to enable seamless integration between LLM applications and external data sources and tools.

This library aims to provide a simple and intuitive way to implement MCP servers and clients in Dart, while adhering to the MCP protocol spec. The goal is to make this SDK as similar as possible to the official SDKs available in other languages, ensuring a consistent developer experience across platforms.

Requirements

• Dart SDK version ^3.0.0 or higher

Ensure you have the correct Dart SDK version installed. See https://dart.dev/get-dart for installation instructions.

Features

• Stdio support (Server and Client)
• SSE support (Server only for now)
• Tools
• Resources
• Prompts
• Sampling
• Roots

Getting started

Below code is the simplest way to start the MCP server.

import 'package:mcp_dart/mcp_dart.dart';

void main() async {
  McpServer server = McpServer(
    Implementation(name: "mcp-example-server", version: "1.0.0"),
    options: ServerOptions(
      capabilities: ServerCapabilities(
        resources: ServerCapabilitiesResources(),
        tools: ServerCapabilitiesTools(),
      ),
    ),
  );

  server.tool(
    "calculate",
    description: 'Perform basic arithmetic operations',
    inputSchemaProperties: {
      'operation': {
        'type': 'string',
        'enum': ['add', 'subtract', 'multiply', 'divide'],
      },
      'a': {'type': 'number'},
      'b': {'type': 'number'},
    },
    callback: ({args, extra}) async {
      final operation = args!['operation'];
      final a = args['a'];
      final b = args['b'];
      return CallToolResult(
        content: [
          TextContent(
            text: switch (operation) {
              'add' => 'Result: ${a + b}',
              'subtract' => 'Result: ${a - b}',
              'multiply' => 'Result: ${a * b}',
              'divide' => 'Result: ${a / b}',
              _ => throw Exception('Invalid operation'),
            },
          ),
        ],
      );
    },
  );

  server.connect(StdioServerTransport());
}

Usage

Once you compile your MCP server, you can compile the client using the below code.

dart compile exe example/server_stdio.dart -o ./server_stdio

Or just run it with JIT.

dart run example/server_stdio.dart

To configure it with the client (ex, Claude Desktop), you can use the below code.

{
  "mcpServers": {
    "calculator_jit": {
      "command": "path/to/dart",
      "args": [
        "/path/to/server_stdio.dart"
      ]
    },
    "calculator_aot": {
      "command": "path/to/compiled/server_stdio",
    },
  }
}

More examples

https://github.com/leehack/mcp_dart/tree/main/example

Credits

This library is inspired by the following projects:

• https://github.com/crbrotea/dart_mcp
• https://github.com/nmfisher/simple_dart_mcp_server