CALCULATE_MCP

Deterministic calculation tools for LLMs via the Model Context Protocol (MCP).

Instead of asking a language model to do arithmetic in hidden reasoning, CALCULATE_MCP gives it explicit deterministic tools for arithmetic, high-precision decimals, units, statistics, finance, matrices, complex numbers, numerical calculus, probability distributions, date math, and root solving.

Built for the 2026 MCP TypeScript SDK v2 and usable over both Streamable HTTP and stdio.

Tools

Related MCP server: Math-MCP

Why another calculator MCP?

The point is not to replace a pocket calculator. The point is to give an LLM a deterministic numerical execution layer that it can call whenever a response depends on exact arithmetic or repeatable numerical methods.

The expression evaluator does not use JavaScript eval. Expressions are parsed by a dedicated math parser with assignment, logical expressions, conditionals, concatenation, and membership operators disabled.

For decimal-sensitive work such as 0.1 + 0.2, use calculate_decimal:

{
  "operation": "add",
  "a": "0.1",
  "b": "0.2",
  "precision": 50
}

Result: 0.3.

Advanced examples

Matrix solve:

{
  "operation": "solve",
  "a": [[2, 1], [1, -1]],
  "b": [5, 1]
}

Numerical derivative:

{
  "operation": "derivative",
  "expression": "x^3",
  "x": 2
}

Normal CDF:

{
  "distribution": "normal",
  "operation": "cdf",
  "params": { "x": 1.96, "mean": 0, "sd": 1 }
}

Date math uses YYYY-MM-DD and UTC calendar semantics. business_days counts Monday-Friday and does not remove public holidays.

Run over HTTP

Requires Node.js 22+.

npm install
npm run build
npm start

MCP endpoint: http://localhost:3000/mcp
Health check: GET /health

Environment variables:

For public deployment, set ALLOWED_HOSTS, for example:

ALLOWED_HOSTS=calculate.example.com npm start

Run over stdio

npm install
npm run build
npm run start:stdio

Example local MCP client configuration:

{
  "mcpServers": {
    "calculate": {
      "command": "node",
      "args": ["/absolute/path/to/CALCULATE_MCP/dist/src/stdio.js"]
    }
  }
}

Expression syntax

Examples:

2 + 3 * 4
sqrt(2)^2
sin(pi / 2)
log10(1000)
a*b + c
x^3 - x - 2

Constants: pi, e, tau.

Functions include abs, sqrt, sin, cos, tan, inverse/hyperbolic trig, ln, log10, log2, exp, min, max, hypot, floor, ceil, round, trunc, and sign.

Supported units

Call list_units for the machine-readable list. Categories include length, mass, time, area, volume, speed, data size, and temperature.

Numerical-method notes

• Matrix inverse/solve use Gaussian elimination with partial pivoting.

• Derivatives use a five-point central difference.

• Definite integrals use Simpson's rule.

• Root solving uses bisection and requires a sign-changing bracket.

• Probability functions are deterministic numerical implementations; they are not intended as a replacement for specialized high-precision statistical libraries in extreme-tail scientific work.

Development

npm install
npm run check
npm test
npm run build

License

MIT