MCP(Model Context Protocol) for Dart #

The Model Context Protocol (MCP) is a standardized protocol for communication between AI applications and external services. It enables:

• Tools: Allow AI to execute actions (API calls, computations, etc.)
• Resources: Provide context and data to AI (files, databases, APIs)
• Prompts: Pre-built prompt templates with arguments

Understanding MCP: Client, Server, and Host #

MCP follows a client-server architecture with three key components:

• MCP Host: The AI application that provides the user interface and manages connections to multiple MCP servers.

  • Example: Claude Desktop, IDEs like VS Code, custom AI applications
  • Manages server lifecycle, discovers capabilities, and orchestrates interactions

• MCP Client: The protocol implementation within the host that communicates with servers.

  • Handles protocol negotiation, capability discovery, and request/response flow
  • Typically built into or used by the MCP host

• MCP Server: Provides capabilities (tools, resources, prompts) that AI can use through the host.

  • Example: Servers for file system access, database queries, or API integrations
  • Runs as a separate process and communicates via standardized transports (stdio, StreamableHTTP)

Typical Flow: User ↔ MCP Host (with Client) ↔ MCP Protocol ↔ Your Server ↔ External Services/Data

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.

What This SDK Provides #

This SDK lets you build both MCP servers and clients in Dart/Flutter.

• ✅ Build MCP Servers - Create servers that expose tools, resources, and prompts to AI hosts
• ✅ Build MCP Clients - Create AI applications that can connect to and use MCP servers
• ✅ Full MCP Protocol Support - Complete MCP specification 2025-06-18 implementation
• ✅ Multiple Transport Options - Stdio, StreamableHTTP, Stream, or custom transports
• ✅ All Capabilities - Tools, Resources, Prompts, Sampling, Roots, Completions, Elicitation
• ✅ OAuth2 Support - Complete authentication with PKCE
• ✅ Type-Safe - Comprehensive type definitions with null safety
• ✅ Cross-Platform - Works on VM, Web, and Flutter

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.

Model Context Protocol Version #

The current version of the protocol is 2025-06-18. This library is designed to be compatible with this version, and any future updates will be made to ensure continued compatibility.

It's also backward compatible with previous versions including 2025-03-26, 2024-11-05, and 2024-10-07.

New in 2025-06-18: Elicitation support for server-initiated user input collection.

Documentation #

Getting Started #

• 📖 Quick Start Guide - Get up and running in 5 minutes
• 🔧 Server Guide - Complete guide to building MCP servers
• 💻 Client Guide - Complete guide to building MCP clients

Core Concepts #

• 🛠️ Tools Documentation - Implementing executable tools
• 🔌 Transport Options - Built-in and custom transport implementations
• 📚 Examples - Real-world usage examples
• ⚡ Quick Reference - Fast lookup guide

Advanced Features #

• 🔐 OAuth Authentication - OAuth2 guides and examples
• 📝 For resources, prompts, and other features, see the Server and Client guides

Quick Start Example #

Below is the simplest way to create an 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',
    toolInputSchema: ToolInputSchema(
      properties: {
        'operation': {
          'type': 'string',
          'enum': ['add', 'subtract', 'multiply', 'divide'],
        },
        'a': {'type': 'number'},
        'b': {'type': 'number'},
      },
      required: ['operation', 'a', 'b'],
    ),
    callback: ({args, extra}) async {
      final operation = args!['operation'];
      final a = args['a'];
      final b = args['b'];
      return CallToolResult.fromContent(
        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());
}

Running Your Server #

Compile your MCP server to an executable:

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

Or run it directly with JIT:

dart run example/server_stdio.dart

Connecting to AI Hosts #

To configure your server with AI hosts like Claude Desktop:

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

Authentication #

This library supports OAuth2 authentication with PKCE for both clients and servers. For complete authentication guides and examples, see the OAuth Authentication documentation.

Platform Support #

Custom Transports: You can implement your own transport layer by extending the transport interfaces if you need specific communication patterns not covered by the built-in options.

More Examples #

For additional examples including authentication, HTTP clients, and advanced features:

• All Examples
• Authentication Examples

Community & Support #

• Issues & Bug Reports: GitHub Issues
• Package: pub.dev/packages/mcp_dart
• Protocol Spec: MCP Specification

Credits #

This library is inspired by the following projects:

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