MCP Example Server

This is a Model Context Protocol (MCP) server that provides two main categories of tools:

1. Database Tools - For interacting with a SQLite database
2. Calculator Tools - For performing mathematical calculations

Features

Database Tools

• query_database - Execute custom SQL queries
• get_all_users - Retrieve all users with optional limit
• get_user_by_id - Get a specific user by ID
• add_user - Add a new user to the database
• update_user - Update an existing user
• delete_user - Delete a user from the database

Calculator Tools

• calculate - Perform basic mathematical operations (add, subtract, multiply, divide, power, sqrt, sin, cos, tan, log, abs, round, floor, ceil)
• calculate_expression - Evaluate mathematical expressions
• calculate_stats - Calculate statistical measures (mean, median, variance, standard deviation, etc.)

Installation

1. Install dependencies:

npm install

2. The database will be automatically created when you first run the server.

Usage

Starting the Server

npm start

Or for development with auto-restart:

npm run dev

Database Schema

The server creates a SQLite database with the following schema:

CREATE TABLE users (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  name TEXT NOT NULL,
  email TEXT UNIQUE NOT NULL,
  age INTEGER,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

Sample data is automatically inserted when the database is first created.

Tool Examples

Database Operations

1. Get all users:

{
  "name": "get_all_users",
  "arguments": {}
}

2. Get user by ID:

{
  "name": "get_user_by_id",
  "arguments": {
    "id": 1
  }
}

3. Add a new user:

{
  "name": "add_user",
  "arguments": {
    "name": "John Doe",
    "email": "john@example.com",
    "age": 30
  }
}

4. Execute custom query:

{
  "name": "query_database",
  "arguments": {
    "query": "SELECT * FROM users WHERE age > 25"
  }
}

Calculator Operations

1. Basic calculation:

{
  "name": "calculate",
  "arguments": {
    "operation": "add",
    "numbers": [5, 3]
  }
}

2. Evaluate expression:

{
  "name": "calculate_expression",
  "arguments": {
    "expression": "2 + 3 * 4"
  }
}

3. Statistical analysis:

{
  "name": "calculate_stats",
  "arguments": {
    "numbers": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  }
}

Available Calculator Operations

• add - Addition
• subtract - Subtraction
• multiply - Multiplication
• divide - Division (with zero check)
• power - Exponentiation
• sqrt - Square root
• sin - Sine function
• cos - Cosine function
• tan - Tangent function
• log - Natural logarithm
• abs - Absolute value
• round - Round to nearest integer
• floor - Floor function
• ceil - Ceiling function

Project Structure

├── package.json
├── README.md
├── src/
│   ├── server.js      # Main MCP server
│   ├── database.js    # Database operations
│   └── calculator.js  # Calculator operations
└── data/
    └── example.db     # SQLite database (created automatically)

Error Handling

The server includes comprehensive error handling for:

• Invalid SQL queries
• Database connection issues
• Mathematical operation errors (division by zero, invalid inputs)
• Missing required parameters
• Unknown tool names

Development

To modify or extend the server:

1. Add new tools in the setupTools() method in server.js
2. Implement corresponding handler methods
3. Update the tools list in the tools/list handler
4. Add any necessary database operations in database.js
5. Add calculator functions in calculator.js

Dependencies

• @modelcontextprotocol/sdk - MCP SDK for Node.js
• sqlite3 - SQLite database driver
• express - Web framework (for potential future HTTP transport)

License

MIT