MCP Csharp Create

MCP C# Server Creation Guide

Overview

Create MCP (Model Context Protocol) servers using the official C# SDK and Microsoft project templates. This skill covers project scaffolding, tool/prompt/resource registration, and transport configuration for both local (stdio) and remote (HTTP) scenarios.

Process

🚀 High-Level Workflow

Phase 1: Project Setup

1.1 Prerequisites

Ensure you have the following installed:

• .NET 10.0 SDK or later (Download)
• Visual Studio 2022+ or Visual Studio Code with C# Dev Kit
• GitHub Copilot (optional, for Agent Mode testing)

1.2 Install/Update the MCP Server Template

# Installs if missing, updates if outdated (idempotent)
dotnet new install Microsoft.McpServer.ProjectTemplates

Note: This command is safe to run anytime - it installs the template if missing, or updates to the latest version if already installed.

1.3 Choose Your Transport

⚠️ ASK THE USER: Before proceeding, ask which transport type they need:

"Which transport type do you need for your MCP server?"

• stdio - Local/CLI integration, runs as subprocess (simpler, recommended for getting started)
• HTTP - Remote/web service, multiple clients, cloud deployment

Decision Guide:

Default recommendation: If the user is unsure, recommend stdio - it's simpler and works great for most local development scenarios. They can always create an HTTP version later.

1.4 Create a New MCP Server Project

For stdio transport (local/CLI integrations):

dotnet new mcpserver -n MyMcpServer

For HTTP transport (remote/web services):

dotnet new mcpserver -n MyMcpServer --transport http

Template Options:

Phase 2: Implementation

2.1 Project Structure

The template creates the following structure:

stdio transport:

MyMcpServer/
├── MyMcpServer.csproj
├── Program.cs
├── Tools/
│   └── RandomNumberTools.cs
└── server.json

HTTP transport:

MyMcpServer/
├── MyMcpServer.csproj
├── Program.cs
├── Tools/
│   └── RandomNumberTools.cs
├── MyMcpServer.http
└── server.json

2.2 Implement Tools

Tools are the primary way MCP servers expose functionality to LLMs. Use the [McpServerToolType] and [McpServerTool] attributes:

using ModelContextProtocol.Server;
using System.ComponentModel;

[McpServerToolType]
public static class MyTools
{
    [McpServerTool, Description("Searches for users by name or email.")]
    public static async Task<string> SearchUsers(
        [Description("Search query string")] string query,
        [Description("Maximum results to return (1-100)")] int limit = 20,
        CancellationToken cancellationToken = default)
    {
        // Implementation here
        return $"Found users matching '{query}'";
    }
}

Load 📋 C# MCP Server Guide for complete implementation patterns.

2.3 Implement Prompts (Optional)

Prompts provide reusable templates for LLM interactions:

using Microsoft.Extensions.AI;
using ModelContextProtocol.Server;
using System.ComponentModel;

[McpServerPromptType]
public static class MyPrompts
{
    [McpServerPrompt, Description("Creates a prompt to summarize content.")]
    public static ChatMessage Summarize(
        [Description("The content to summarize")] string content) =>
        new(ChatRole.User, $"Please summarize this content into a single sentence: {content}");
}

2.4 Configure Transport

stdio (Program.cs):

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

var builder = Host.CreateApplicationBuilder(args);
builder.Logging.AddConsole(options =>
{
    // CRITICAL: Log to stderr for stdio transport
    options.LogToStandardErrorThreshold = LogLevel.Trace;
});

builder.Services
    .AddMcpServer()
    .WithStdioServerTransport()
    .WithToolsFromAssembly();

await builder.Build().RunAsync();

HTTP (Program.cs):

using ModelContextProtocol.Server;
using System.ComponentModel;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddMcpServer()
    .WithHttpTransport()
    .WithToolsFromAssembly();

var app = builder.Build();
app.MapMcp();
app.Run("http://localhost:3001");

Phase 3: Best Practices

Load 📋 C# Best Practices for naming conventions, response formats, and security guidelines.

Key principles:

• Use [Description] attributes on all tools and parameters
• Include service prefix in tool names (e.g., github_create_issue)
• Support both JSON and Markdown response formats
• Implement pagination for list operations
• Handle errors with actionable messages

Related Skills

• mcp-csharp-debug - Running and debugging your MCP server
• mcp-csharp-test - Testing and evaluation creation
• mcp-csharp-publish - Publishing to NuGet, Docker, and Azure

Reference Files

📚 Documentation Library

Core Documentation

• 📋 C# MCP Server Implementation Guide - Complete patterns for tools, prompts, resources, and transports
• 📋 C# Best Practices - Naming conventions, response formats, security

SDK Documentation

• C# SDK: Fetch from https://raw.githubusercontent.com/modelcontextprotocol/csharp-sdk/main/README.md
• ASP.NET Core Extensions: Fetch from https://raw.githubusercontent.com/modelcontextprotocol/csharp-sdk/main/src/ModelContextProtocol.AspNetCore/README.md
• Microsoft Template Guide: https://learn.microsoft.com/en-us/dotnet/ai/quickstarts/build-mcp-server

MCP Protocol

• MCP Specification: Start with sitemap at https://modelcontextprotocol.io/sitemap.xml, then fetch specific pages with .md suffix