Concatenating Calculator Server

An MCP (Model Context Protocol) server that redefines addition — when asked to add two numbers, it concatenates them instead.

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📖 Overview

This is a custom Model Context Protocol (MCP) server that exposes an add_numbers tool. Rather than performing arithmetic addition, the tool concatenates the two inputs as strings.

Example:

Input:  add_numbers(3, 5)
Output: "35"

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✨ Features

• Implements the MCP server specification
• Exposes a single add_numbers tool
• Concatenates two numbers as strings instead of summing them
• Compatible with any MCP-capable client (e.g. Claude for Desktop)

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🚀 Getting Started

Prerequisites

• Node.js v18+ (or your relevant runtime)
• An MCP-compatible client, such as Claude for Desktop

Installation

1. Clone the repository:

   git clone https://github.com/yash312312/custom-mcp-server.git
   

2. Install dependencies:

   npm install
   

3. Build the project:

   npm run build
   

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🔧 Configuration

To connect this server to Claude for Desktop, add the following to your claude_desktop_config.json:

{
  "mcpServers": {
    "mcp-server": {
      "command": "node",
      "args": ["/absolute/path/to/your/build/index.js"]
    }
  }
}

💡 Replace /absolute/path/to/your/build/index.js with the actual path on your machine, which is the generated build folder inside the directory.

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🛠️ Tool Reference

add_numbers

Concatenates two numbers together as a string.

Parameter	Type	Description
a	number	The first number
b	number	The second number

Returns: A string containing a and b concatenated.

Example:

add_numbers(12, 34)  →  "1234"
add_numbers(0, 7)    →  "07"

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📁 Project Structure

.
├── src/
│   └── index.ts        # MCP server entry point
├── build/              # Compiled output
├── package.json
└── README.md

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🧪 Running Locally

You can test the server directly without a client:

node build/index.js

The server will start and await MCP-compatible input over stdio.

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🤝 Contributing

Contributions, issues, and feature requests are welcome! Feel free to open a GitHub Issue or submit a pull request.

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📄 License

This project is licensed under the MIT License.

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🙋 Acknowledgements

Built using the Model Context Protocol SDK by Anthropic.