📌Overview

Purpose: MCPSharp is designed to facilitate the development of Model Context Protocol (MCP) servers and clients, providing a standardized API for AI assistants and models.

Overview: MCPSharp is a robust .NET library that allows developers to create and expose MCP-compliant tools and APIs seamlessly. It abstracts the complexities of the MCP protocol, enabling easy integration with AI functionality in applications while supporting a flexible and attribute-based programming model.

Key Features:

Easy-to-use Attribute-based API: Developers can easily define tools and resources using attributes like [McpTool], simplifying the process of creating MCP endpoints.
Built-in JSON-RPC Support: Automatic handling of request and response communication streamlines interactions with the server, eliminating the need for extensive boilerplate code.
Dynamic Tool Registration: Allows for on-the-fly registration of tools, accommodating custom implementations and enhancing flexibility in tool management.
Error Handling & Complex Object Support: Improved error handling features provide detailed insights during development, while enhanced support for complex object parameters simplifies interactions.
Integration with Microsoft.Extensions.AI and Semantic Kernel: MCPSharp allows broad compatibility with existing AI frameworks, making it easier to enhance applications with advanced AI capabilities.

MCPSharp

MCPSharp is a .NET library for building Model Context Protocol (MCP) servers and clients used by AI assistants and models. With MCPSharp, you can:

Create MCP-compliant tools and functions for AI models
Connect to existing MCP servers from C# code
Expose your .NET methods as MCP endpoints
Handle MCP protocol details and JSON-RPC communication seamlessly

What's New in MCPSharp

Microsoft.Extensions.AI Integration: Tools can now be exposed as AIFunctions
Semantic Kernel Support: Add tools with Semantic Kernel's KernelFunctionAttribute
Dynamic Tool Registration: Register tools dynamically with custom logic
Tool Change Notifications: Clients notified of updates to tools
Complex Object Parameter Support: Improved handling of complex objects
Better Error Handling: Enhanced error management with detailed stack traces

When to Use MCPSharp

Use MCPSharp to:

Create tools for AI assistants like Claude Desktop
Build MCP-compliant APIs without dealing with protocol details
Expose existing .NET code as MCP endpoints
Add standardized AI capabilities to applications

Features

Attribute-based API ([McpTool], [McpResource])
Built-in JSON-RPC support
Automatic parameter validation
Rich documentation support with XML comments
Minimal configuration required for basic usage

Prerequisites

.NET Standard 2.0 or later

Installation

dotnet add package MCPSharp

Quick Start

1. Define a Tool

Create a class and mark methods with the [McpTool] attribute:

using MCPSharp;

public class Calculator
{
    [McpTool("add", "Adds two numbers")]
    public static int Add([McpParameter(true)] int a, [McpParameter(true)] int b)
    {
        return a + b;
    }
}

2. Start the Server

await MCPServer.StartAsync("CalculatorServer", "1.0.0");

Advanced Usage

Dynamic Tool Registration

MCPServer.AddToolHandler(new Tool() 
{
    Name = "dynamicTool",
    Description = "A dynamic tool",
    InputSchema = new InputSchema {
        Type = "object",
        Required = ["input"],
        Properties = new Dictionary<string, ParameterSchema>{
            {"input", new ParameterSchema{Type="string", Description="Input value"}}
        }
    }
}, (string input) => { return $"You provided: {input}"; });

Use with Microsoft.Extensions.AI

MCPClient client = new("AIClient", "1.0", "path/to/mcp/server");
IList<AIFunction> functions = await client.GetFunctionsAsync();

Semantic Kernel Integration

using Microsoft.SemanticKernel;

public class MySkillClass
{
    [KernelFunction("MyFunction")]
    [Description("Description of my function")]
    public string MyFunction(string input) => $"Processed: {input}";
}

// Register with MCPServer
MCPServer.Register<MySkillClass>();

API Reference

Attributes

[McpTool] - Marks a method as an MCP tool
[McpParameter] - Provides metadata for function parameters
[McpResource] - Marks a property or method as an MCP resource

Server Methods

MCPServer.StartAsync(string serverName, string version) - Starts the MCP server
MCPServer.Register<T>() - Registers a class containing tools or resources
MCPServer.AddToolHandler(Tool tool, Delegate func) - Registers a dynamic tool

Client Methods

new MCPClient(string name, string version, string server) - Create a client instance
client.GetToolsAsync() - Get available tools
client.CallToolAsync(string name, Dictionary<string, object> parameters) - Call a tool
client.GetResourcesAsync() - Get available resources
client.GetFunctionsAsync() - Get tools as AIFunctions

XML Documentation Support

MCPSharp automatically extracts documentation from XML comments:

/// <summary>
/// Provides mathematical operations
/// </summary>
public class Calculator
{
    /// <summary>
    /// Adds two numbers together
    /// </summary>
    [McpTool]
    public static int Add([McpParameter(true)] int a, [McpParameter(true)] int b)
    {
        return a + b;
    }
}

Enable XML documentation in your project file:

<PropertyGroup>
    <GenerateDocumentationFile>true</GenerateDocumentationFile>
    <NoWarn>$(NoWarn);1591</NoWarn>
</PropertyGroup>

Migration Notes

[McpFunction] is deprecated; use [McpTool] instead
Use MCPServer.Register<T>() for consistency

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License.