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Calc MCP

Local MCP server with 21 tools for deterministic calculations, dates, encoding, hashing, parsing, conversion, and random generation.

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Install Calc MCP

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": {
    "calc-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@coo-quack/calc-mcp@2.1.2"
      ]
    }
  }
}

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

Automated check passed— started and listed 21 tools correctly (Today).

Overview

The calc-mcp MCP server exposes 21 local tools for deterministic math, date and timezone operations, encoding, hashing, parsing, conversion, and random generation. It runs through Node.js and communicates with MCP-compatible clients over the standard command-line setup, without an API key or external service. Reach for it when an agent needs reproducible calculations, cryptographically random values, accurate date handling, or structured utility operations.

Use cases

  • Evaluate arithmetic and statistics without relying on model-generated calculations
  • Calculate date offsets and convert times across timezones
  • Generate UUIDs, passwords, random values, and shuffled lists
  • Encode, decode, hash, validate, and parse developer data
  • Convert units, colors, number bases, and semantic versions

Key features

  • 21 local MCP tools
  • Deterministic math and date operations
  • Cryptographic randomness and hashing
  • Encoding, parsing, and format validation
  • Unit, color, IP, and number-base conversion
  • No API key or external service required

Tools21

What Calc MCP lets your agent do. Expand a tool for its parameters.

Verified live~3.1k tokens of context

Security & health

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

ActiveLast checked 2d ago

Recent health check succeeded.

8/8 checks healthy over the last 44d

What it can do

From the 21 tools this server returned when we ran it.

Handles credentials · 2Makes network requests · 2Read-only tools · 21
Network at startup3 connections
Files written at startupNone
Install scriptsNone
npm provenanceSigned build
Package age257 days
Maintainers1

Observed 2026-10-26 in an isolated sandbox. A description of reach, not a security audit.

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 3d ago via OSV.dev · @coo-quack/calc-mcp@2.1.2 (npm)

Adoption & maintenance

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

GitHub stars9Stargazers on the source repository.
npm downloads1kPackage downloads in the last 30 days.
Last commit2d agoMost recent push to the default branch.
Availability100%Our rolling endpoint + install checks that succeeded.
Install checkPassedOur sandbox started it and listed its tools.
Tools exposed21Callable tools this server registers over MCP.

How Calc MCP works

What calc-mcp MCP server does

The calc-mcp MCP server gives an MCP-compatible AI client a collection of local utility tools instead of requiring the model to perform these operations itself. Its 21 tools cover numerical work, text processing, dates, random generation, encoding, validation, parsing, and common developer conversions.

The server is suited to tasks where an incorrect guess is undesirable: evaluating expressions, calculating date offsets, converting timezones, producing UUIDs, hashing input, checking a Luhn number, or interpreting a cron expression. Computation runs locally, and the project states that no data is sent to external services.

How it works

Run the package with Node.js and register the command with an MCP client. The client exposes the available tools to the assistant, which can select one based on a natural-language request. A typical launch command uses npx and the published package:

Terminal
npx -y @coo-quack/calc-mcp@2.1.2

The project also documents a Claude Code registration command:

Terminal
claude mcp add -s user calc-mcp -- npx -y @coo-quack/calc-mcp@2.1.2

The operations are designed to be deterministic where the input permits it. Random-generation operations are an exception by design and provide UUIDs, ULIDs, passwords, random numbers, and shuffles.

Setup and configuration

Node.js is required. The package can be started directly with npx, and the MCP client must be configured to launch it.

The documented client coverage includes Claude Code, Claude Desktop, VS Code Copilot, Cursor, and Windsurf. The package is presented as usable with MCP clients generally, provided they can launch a standard command-based server.

Tools and capabilities

The calc-mcp MCP server includes these tool groups:

  • math evaluates expressions and performs statistics; base converts numbers between bases 2 through 36.
  • datetime handles current time, timezone conversion, and Unix timestamps; date calculates differences, additions, subtractions, weekdays, and wareki dates.
  • random generates UUID v4/v7 values, ULIDs, passwords, random numbers, and shuffles; luhn validates numbers and generates check digits.
  • hash supports MD5, SHA-1, SHA-256, SHA-512, CRC32, and HMAC; base64 encodes and decodes Base64 data.
  • encode handles URL encoding, HTML entities, and Unicode escapes; count measures grapheme-aware characters, words, lines, and bytes.
  • regex tests, matches, replaces, and finds all matches; diff produces line differences and Levenshtein distances.
  • format_validate checks JSON, CSV, XML, and YAML; cron_parse describes cron schedules and calculates upcoming runs.
  • ip provides IPv4 and IPv6 details, CIDR checks, and ranges; color converts HEX, RGB, and HSL values, including alpha channels.
  • convert covers eight unit categories and 146 unit names; char_info reports Unicode code points, blocks, and categories.
  • jwt_decode reads JWT headers and payloads without verification; url_parse separates URL components; semver validates, compares, parses, and evaluates version ranges.

Limitations and notes

JWT decoding does not verify signatures, so it should not be treated as authentication or token validation. The server performs local utility operations rather than connecting to a remote database, API, or hosted computation service. Random outputs are intentionally non-repeatable, while deterministic tools return results based on their inputs.

Read the full README View source on GitHub

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Frequently Asked Questions about Calc MCP

calc-mcp is an MCP server that connects MCP-compatible AI clients to 21 local tools for math, dates, randomness, encoding, hashing, parsing, validation, conversion, and text analysis. It runs with Node.js, requires no API key, and performs computations locally so agents can use deterministic utility operations.

Install it by registering `npx -y @coo-quack/calc-mcp@2.1.2` with your MCP client. For Claude Code, use `claude mcp add -s user calc-mcp -- npx -y @coo-quack/calc-mcp@2.1.2`. Node.js is required.

Configure Cursor to launch the package command through its MCP settings; the project also lists Claude Desktop, VS Code Copilot, Windsurf, and Claude Code.

No, calc-mcp does not require an account or API key. It runs locally through Node.js and communicates with the configured MCP client.

No, calc-mcp only decodes JWT headers and payloads; it does not verify signatures. Use the `jwt_decode` tool for inspection, not authentication or token validation.

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