Calc MCP

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Calc MCP21 tools for things AI is not good at

Deterministic math, cryptographic randomness, accurate date arithmetic, encoding, hashing, and more

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🧮

Precise Math

No more hallucinated calculations. Evaluate complex expressions with mathjs, compute statistics, all deterministic.

🎲

True Randomness

Cryptographically secure UUIDs, ULIDs, passwords, and shuffling. No fake random numbers from AI.

📅

Accurate Dates

Timezone conversion, date arithmetic, cron parsing. No more guessing what day it is 100 days from now.

🔐

Hashing & Encoding

SHA-256, Base64, URL encoding, JWT decoding. Real cryptographic operations, not hallucinated hashes.

🌈

Conversions

8 categories, 72 units. Length, weight, temperature, area, volume, speed, data, time. Including Japanese units (tsubo, tatami).

🔍

Parsing & Validation

IP addresses, URLs, JSON, semver, Luhn checksums. Deterministic validation and parsing.

Why Calc MCP? ​

LLMs are incredible at natural language understanding, but terrible at things that require precision.

AI aloneWith calc-mcp
"10 + 34 × 341 ÷ 23 = 507.8" ❌514.087 ✅ (math)
"Here's a UUID: 550e8400-..." 🤷 fakeCryptographically random UUID v4/v7 ✅ (random)
"100 days from now is..." 🤔 guess2026-05-22 ✅ (date)
"SHA-256 of password123 is..." 💀 hallucinatedef92b778bafe... ✅ (hash)

Calc MCP gives your AI assistant the tools to delegate these tasks to deterministic, tested code.

  • Deterministic — Same input, same correct output, every time. No more "it depends on the run."
  • Secure — Sandboxed math evaluation, ReDoS protection, weak hash warnings built in.
  • Private — All computation runs locally. No data sent to external services.
  • Zero config — Install once, just ask in natural language. The AI picks the right tool.
  • No API key — Works offline, no external dependencies. Just Node.js.

Quick Start ​

bash
# Claude Code
claude mcp add -s user calc-mcp -- npx --prefix /tmp -y @coo-quack/calc-mcp@latest

Works with Claude Desktop, VS Code Copilot, Cursor, Windsurf — see installation guides.

Usage ​

Just ask in natural language. The AI picks the right tool automatically:

You: What's 10 + 34 × 341 ÷ 23?
AI: [uses math tool] → 514.087

You: Generate a UUID v7
AI: [uses random tool] → 019c4b54-aad2-7e52-8a3b-...

You: What's 100 days after 2026-02-11?
AI: [uses date tool] → 2026-05-22

You: SHA-256 hash of "password123"
AI: [uses hash tool] → ef92b778bafe771e89245b89ec...

See more examples →

All 21 Tools ​

CategoryTools
Mathmath, count, convert, base
Randomrandom (UUID, ULID, password, number, shuffle)
Datesdatetime, date, cron_parse
Textbase64, encode, hash, regex, diff, char_info
Validationjson_validate, luhn, semver
Parsingip, color, jwt_decode, url_parse

View all tools →

Features ​

  • ✅ 21 MCP tools covering calculations, randomness, dates, encoding, parsing
  • ✅ Tested — 453 tests, 512 assertions across unit and E2E
  • ✅ Fast — Pure JavaScript/TypeScript, no heavy dependencies
  • ✅ Cross-platform — Works with Claude Desktop, VS Code, Cursor, Windsurf
  • ✅ MIT Licensed — Free to use, modify, distribute

Released under the MIT License.

Copyright © 2026 coo-quack