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Cruncher

Scientific calculator over MCP with arithmetic, statistics, trigonometry, constants, memory, and 80+ unit conversions.

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Install Cruncher

Pick your client, then add it in one click or paste the config.

STDIONode.js
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "cruncher": {
      "command": "npx",
      "args": [
        "-y",
        "@slbdn/cruncher-mcp"
      ],
      "env": {
        "CRUNCHER_TIMEOUT": "YOUR_VALUE_HERE",
        "CRUNCHER_TOOL_SET": "YOUR_VALUE_HERE"
      }
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

Values are written into the snippet above so you can paste it as is. They never leave your browser.

We couldn’t confirm it starts correctly

The install command started, but didn't respond the way we expected when we tried to talk to it.

npx -y @slbdn/cruncher-mcp

initialize succeeded but no response to tools/list.

This is an experimental automated check and can have false negatives — missing environment variables, a slow cold install, etc. It doesn’t necessarily mean something’s wrong. Last checked 7d ago.

Overview

Cruncher MCP server gives compatible AI clients a Node.js-based scientific calculator through the Model Context Protocol. It exposes tools for arithmetic, expressions, trigonometry, logarithms, statistics, percentages, constants, memory, and unit conversion. The server communicates over stdio and validates requests with custom JSON Schema handling. Use it when an agent needs reproducible calculations without connecting to an external math service.

Use cases

  • Evaluate expressions and arithmetic in an AI workflow
  • Calculate descriptive statistics for numeric arrays
  • Convert measurements across supported unit categories
  • Look up mathematical, physical, and chemical constants
  • Perform trigonometric calculations in degrees or radians

Key features

  • 43 scientific calculator tools
  • Arithmetic and safe expression evaluation
  • Statistics, percentages, and trigonometry
  • 80+ unit conversions across eight categories
  • Scientific constants and optional calculator memory
  • Tiered tool exposure with configurable timeouts

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked Today

Recent health check succeeded.

8/8 checks healthy over the last 46d

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 1d ago via OSV.dev · @slbdn/cruncher-mcp (npm)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

GitHub stars1Stargazers on the source repository.
npm downloads174Package downloads in the last 30 days.
Last commit3mo agoMost recent push to the default branch.
Install checkInconclusiveStarted but did not complete the MCP handshake in our test.
Directory activity1 viewsConfig copies, upvotes, and views on AllMCPs.

How Cruncher works

What Cruncher does

The Cruncher MCP server exposes scientific calculator functions to MCP-compatible AI clients. Its tools cover basic arithmetic, complete expression evaluation, powers, square roots, factorials, trigonometric functions, logarithms, percentages, statistics, constants, and absolute values. Trigonometric operations accept degrees or radians.

Statistical tools operate on arrays of numbers and include sum, average, median, minimum, maximum, range, count, variance, and standard deviation. Unit conversion supports more than 80 conversions across length, weight, temperature, area, volume, time, speed, and digital storage. The full tool tier also provides calculator-style memory operations: add to memory, subtract from memory, recall, and clear.

How it works

Cruncher runs as a stdio MCP server implemented in plain JavaScript and uses Node.js standard libraries rather than the official MCP SDK or external math packages. It handles MCP initialization, tool discovery, tool calls, JSON-RPC messages, input validation, and error formatting directly in the application.

Expression evaluation is restricted by a whitelist so accepted input contains numbers and supported mathematical operators rather than arbitrary JavaScript. Calculations run in worker threads, allowing the main process to stop work that exceeds the configured timeout. Decimal operations use integer scaling to reduce common floating-point errors such as the usual JavaScript result for 0.1 + 0.2.

Setup and configuration

Node.js 18 or newer is required. The npm package can be started with npx @slbdn/cruncher-mcp, or the cruncher.js file can be run directly with Node.js. MCP clients need a stdio configuration with either npx and the package name or node and the script path.

The Cruncher MCP server supports three tool exposure levels: minimal, standard, and full. standard is the default and can be selected with CRUNCHER_TOOL_SET. Set CRUNCHER_TIMEOUT to change the calculation timeout in milliseconds; the documented default is three seconds.

The README provides configuration examples for Claude Desktop, Cursor, and Cline, and also documents stdio setup for OpenWebUI. After changing a client configuration, restart the client so it reconnects to the server.

Tools and capabilities

  • Arithmetic: addition, subtraction, multiplication, division, and modulo
  • Expressions, powers, roots, factorials, and absolute values
  • Trigonometry in degrees or radians
  • Base-10 and natural logarithms
  • Array statistics and percentage calculations
  • Mathematical, physical, and chemical constants
  • More than 80 unit conversions in eight categories
  • Memory operations in the full tool tier
  • Tiered tool exposure to control context usage

Limitations and notes

Heavy or very large calculations can be terminated when they exceed the timeout. Memory functions are available only in the full tier. Running the server requires Node.js 18 or newer.

Read the full README View source on GitHub

Reviews

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Frequently Asked Questions about Cruncher

Cruncher is an MCP server that connects compatible AI clients to a Node.js scientific calculator. Its main tools handle arithmetic, expressions, trigonometry, logarithms, statistics, percentages, constants, unit conversions, and optional calculator memory through the Model Context Protocol over stdio.

Install it by running `npx @slbdn/cruncher-mcp` with Node.js 18 or newer, then add that command to your MCP client’s stdio configuration. Alternatively, download `cruncher.js` and run it with `node`.

Yes, Cruncher works with Cursor through its MCP Servers settings. Add a command-based server using `npx @slbdn/cruncher-mcp`, or run the downloaded script with `node /path/to/cruncher.js`.

Set the `CRUNCHER_TIMEOUT` environment variable to the desired timeout in milliseconds. The documented default is three seconds, and worker-thread calculations that exceed the limit can be terminated.

Set `CRUNCHER_TOOL_SET` to `minimal` or `standard` in the server environment. Cruncher also supports a `full` tier, while `standard` is the default.

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