My MCP Server

My MCP Server

A custom Model Context Protocol (MCP) server with an extensible tool architecture for Claude Code. This server makes it easy to add custom tools that Claude can use during conversations.

Features

• Extensible Architecture: Easy-to-use pattern for adding new tools
• TypeScript: Full type safety with TypeScript
• Example Tools Included: Calculator and Echo tools to demonstrate the pattern
• Production-Ready: Proper error handling and validation with Zod
• Well-Documented: Clear examples and documentation for adding new tools

Available Tools

1. Calculate

Perform basic arithmetic operations (add, subtract, multiply, divide).

Example usage:

• "Calculate 15 + 27"
• "What's 100 divided by 4?"
• "Multiply 8 by 9"

2. Echo

Echo a message back, with optional text transformation (uppercase/lowercase).

Example usage:

• "Echo 'Hello World'"
• "Echo 'test message' in uppercase"
• "Echo 'LOUD TEXT' in lowercase"

Installation

1. Install Dependencies

npm install

2. Build the Project

npm run build

This will compile the TypeScript code to JavaScript in the build/ directory.

3. Configure Claude Code

Add the following configuration to your ~/.claude.json file:

{
  "mcpServers": {
    "my-mcp": {
      "type": "stdio",
      "command": "node",
      "args": ["/Users/martin/src/my-mcp/build/index.js"]
    }
  }
}

Important: Make sure to use the absolute path to your build/index.js file.

4. Restart Claude Code

After updating the configuration, restart Claude Code to load the MCP server.

Adding New Tools

Adding a new tool is simple and follows a consistent pattern:

Step 1: Create a New Tool File

Create a new file in src/tools/ with the naming convention your-tool.tool.ts:

import { z } from "zod";
import type { ToolDefinition } from "../types/index.js";

export const yourTool: ToolDefinition = {
  name: "your_tool_name",
  description: "Description of what your tool does",

  inputSchema: z.object({
    param1: z.string().describe("Description of parameter 1"),
    param2: z.number().optional().describe("Optional parameter 2"),
  }),

  handler: async (args) => {
    // Your tool logic here
    const result = `Processed: ${args.param1}`;

    return {
      content: [{
        type: "text",
        text: result
      }]
    };
  }
};

Step 2: Register the Tool

Add your tool to the registry in src/tools/index.ts:

import { yourTool } from "./your-tool.tool.js";

export const tools: ToolDefinition[] = [
  echoTool,
  calculatorTool,
  yourTool,  // Add your tool here
];

Step 3: Rebuild

npm run build

Step 4: Restart Claude Code

Restart Claude Code to load the new tool.

Step 5: Test

Try using your new tool in a conversation with Claude!

Tool Examples

Simple Text Processing Tool

import { z } from "zod";
import type { ToolDefinition } from "../types/index.js";

export const reverseTool: ToolDefinition = {
  name: "reverse",
  description: "Reverse a string",

  inputSchema: z.object({
    text: z.string().describe("The text to reverse"),
  }),

  handler: async (args) => {
    const reversed = args.text.split("").reverse().join("");

    return {
      content: [{
        type: "text",
        text: reversed
      }]
    };
  }
};

API Call Tool

import { z } from "zod";
import type { ToolDefinition } from "../types/index.js";

export const weatherTool: ToolDefinition = {
  name: "get_weather",
  description: "Get current weather for a location",

  inputSchema: z.object({
    location: z.string().describe("City name or zip code"),
  }),

  handler: async (args) => {
    try {
      // Make API call (example)
      const response = await fetch(
        `https://api.weather.example.com/current?location=${args.location}`
      );
      const data = await response.json();

      return {
        content: [{
          type: "text",
          text: `Weather in ${args.location}: ${data.temperature}°F, ${data.conditions}`
        }]
      };
    } catch (error) {
      return {
        isError: true,
        content: [{
          type: "text",
          text: `Failed to fetch weather: ${error instanceof Error ? error.message : 'Unknown error'}`
        }]
      };
    }
  }
};

Project Structure

my-mcp/
├── src/
│   ├── index.ts                    # Main entry point
│   ├── server.ts                   # Server initialization and request handlers
│   ├── tools/
│   │   ├── index.ts                # Tool registry (add new tools here)
│   │   ├── calculator.tool.ts      # Calculator tool implementation
│   │   └── echo.tool.ts            # Echo tool implementation
│   └── types/
│       └── index.ts                # TypeScript type definitions
├── build/                          # Compiled JavaScript (generated)
├── package.json                    # Project depende