🧮 Calculator MCP Server (C#)

A simple Model Context Protocol (MCP) server written in C# (.NET) that exposes calculator tools (add, multiply) and integrates with Cline (VS Code) for AI-driven tool execution.

This project demonstrates how AI models can securely invoke local C# tools using MCP.

🚀 Features

• ✅ MCP server implemented in C#
• ✅ Attribute-based tool registration
• ✅ Tools:
  • add – Adds two numbers
  • multiply – Multiplies two numbers
• ✅ Integrated with Cline MCP
• ✅ Real-time tool invocation & logging
• ✅ Beginner-friendly & extensible

🏗️ Architecture Overview

Cline (VS Code)
   |
   |  MCP Request
   |
MCP Protocol
   |
Calculator MCP Server (C#)
   |
CalculatorTools.Add / Multiply
   |
Result returned to AI

🖼️ Demo Screenshots

MCP Server Registered in Cline

Tool Invocation & Response

🛠️ Tools Implemented

Add

Adds two numbers together.

Parameters

• a – First number
• b – Second number

Multiply

Multiplies two numbers.

Parameters

• a – First number
• b – Second number

📦 Project Structure

CalculatorMcpServer/
├── CalculatorMcpServer/
│   ├── CalculatorMcpServer.csproj
│   ├── Program.cs
│   ├── CalculatorTools.cs
│   └── ...
├── README.md
├── Chat.png
└── my-csharp-server.png

🔧 MCP Server Configuration (Cline)

Create the following file:

C:\Users\<your-user>\.cline\mcp.json

✅ MCP Configuration

{
  "mcpServers": {
    "my-csharp-server": {
      "command": "dotnet",
      "args": [
        "run",
        "--project",
        "C:/Users/Sandeep/source/repos/CalculatorMcpServer/CalculatorMcpServer/CalculatorMcpServer.csproj",
        "--verbosity",
        "quiet"
      ],
      "timeout": 1800
    }
  }
}

📌 Notes:

• Use forward slashes (/) for Windows paths
• Restart VS Code after updating this file
• Verify MCP server using /mcp in Cline

▶️ Running the Server Manually

dotnet run --project CalculatorMcpServer.csproj

🧪 Testing in Cline

Use the add tool with a=12 and b=30
Use the multiply tool with a=10 and b=20

🧠 Example Tool Code

[McpServerToolType]
public class CalculatorTools
{
    [McpServerTool]
    public static double Add(double a, double b)
    {
        Console.WriteLine($"Add called with a={a}, b={b}");
        return a + b;
    }

    [McpServerTool]
    public static double Multiply(double a, double b)
    {
        Console.WriteLine($"Multiply called with a={a}, b={b}");
        return a * b;
    }
}

📜 License

MIT License