ericvrp/calculator-mcp

Calculator MCP Server

A TypeScript-based MCP server that implements a robust calculator with precise decimal arithmetic. This server demonstrates core MCP concepts by providing arithmetic operations with support for multiple operands and configurable precision using Decimal.js.

Features

Tools

Arithmetic Functions

These functions take an array of at least two numbers and return a single numerical result.

• add - Adds an array of numbers.
• subtract - Subtracts numbers sequentially from the first.
• multiply - Multiplies an array of numbers.
• divide - Divides numbers sequentially. Handles division by zero.

Trigonometric Functions

These functions operate on arrays of numbers and return an array of results. The angles input requires at least one number.

• Basic Trigonometry: sin, cos, tan
  • Input: angles (array of numbers), mode ('radians' or 'degrees', defaults to 'radians').
• Inverse Trigonometry: asin, acos, atan
  • Input: values (array of numbers).
• Hyperbolic Functions: sinh, cosh, tanh
  • Input: values (array of numbers).
• Inverse Hyperbolic Functions: asinh, acosh, atanh
  • Input: values (array of numbers).

Miscellaneous

• set_precision - Configures decimal precision for all subsequent calculations.
  • Takes precision parameter as the number of decimal places.

Development

Install dependencies:

bun install

Run the development server:

bun start

Installation as standalone MCP server

To use with Claude Desktop, add the server config:

On MacOS: ~/Library/Application Support/Claude/claude_desktop_config.json On Windows: %APPDATA%/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "Calculator": {
      "command": "/path/to/calculator-mcp/src/index.ts"
    }
  }
}

Or for Cline VSCode extension, add a modified version of this to your MCP config file:

   "Calculator": {
      "autoApprove": [
        "add",
        "subtract",
        "multiply",
        "divide",
        "set_precision"
      ],
      "disabled": true,
      "timeout": 60,
      "type": "stdio",
      "command": "bun",
      "args": [
        "/path-to-your/calculator-mcp/src/index.ts"
      ]
    }

Installation using Docker

To run the MCP server using Docker, you should first build the image using:

docker build -t calculator-mcp .

Followed by adding this to the (Cline) MCP config file:

    "Calculator (docker)": {
      "autoApprove": [
        "add",
        "subtract",
        "multiply",
        "divide",
        "set_precision"
      ],
      "disabled": false,
      "timeout": 60,
      "type": "stdio",
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "calculator-mcp"
      ]
    }

Debugging

Since MCP servers communicate over stdio, debugging can be challenging. We recommend using the MCP Inspector, which is available as a package script:

bun run inspector

The Inspector will provide a URL to access debugging tools in your browser.