MCP C# SDK

Build MCP clients and servers in .NET with the official C# SDK for the Model Context Protocol

MCP C# SDK

The official C# SDK for the Model Context Protocol, enabling .NET applications, services, and libraries to implement and interact with MCP clients and servers.

The Model Context Protocol (MCP) is an open protocol that standardizes how applications provide context to Large Language Models (LLMs). It enables secure integration between LLMs and various data sources and tools.

Key Features

Build MCP Clients

Connect to any MCP server and access tools, prompts, and resources. Works with stdio, HTTP, and SSE transports.

Create MCP Servers

Expose your .NET functionality as MCP tools with attribute-based discovery and dependency injection support.

Microsoft.Extensions.AI Integration

MCP tools inherit from AIFunction and work seamlessly with any IChatClient implementation.

Multiple Transport Options

Support for stdio (process-based), HTTP, and Server-Sent Events (SSE) transports out of the box.

Hosting & DI Support

Built-in integration with Microsoft.Extensions.Hosting and dependency injection for production-ready servers.

AOT Compatible

Native AOT support for fast startup times and minimal memory footprint in your .NET applications.

Three Packages for Different Needs

The SDK consists of three NuGet packages to match your specific requirements:

ModelContextProtocol.Core

Minimal dependencies

Client and low-level server APIs only. Perfect when you need the smallest footprint.

ModelContextProtocol

Recommended starting point

Hosting, dependency injection, and attribute-based discovery. Ideal for most projects.

ModelContextProtocol.AspNetCore

HTTP server support

ASP.NET Core integration for building HTTP-based MCP servers.

Quick Example

Here’s a complete MCP server in just a few lines of code:

Program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using ModelContextProtocol.Server;
using System.ComponentModel;

var builder = Host.CreateApplicationBuilder(args);
builder.Logging.AddConsole(options =>
{
    options.LogToStandardErrorThreshold = LogLevel.Trace;
});
builder.Services
    .AddMcpServer()
    .WithStdioServerTransport()
    .WithToolsFromAssembly();
await builder.Build().RunAsync();

[McpServerToolType]
public static class EchoTool
{
    [McpServerTool, Description("Echoes the message back to the client.")]
    public static string Echo(string message) => $"hello {message}";
}

Get Started

Installation

Install the SDK packages and choose the right one for your project

Quick Start

Build your first MCP client and server in minutes

Learn More

Official MCP Documentation

Learn about the Model Context Protocol specification

API Documentation

Explore the complete API reference

GitHub Repository

View source code and contribute to the SDK