Calc MCP

📖 Documentation — Full tool reference, examples, and install guides.

21 tools for things AI is not good at — deterministic math, cryptographic randomness, accurate date arithmetic, encoding, hashing, and more.

LLMs hallucinate calculations, can't generate true random numbers, and struggle with timezones. This MCP server fixes that.

Quick Start

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

# Or just run it
npx --prefix /tmp -y @coo-quack/calc-mcp@latest

Works with Claude Desktop, VS Code Copilot, Cursor, Windsurf, and any MCP client — setup guides below.

Why?

| AI alone | With calc-mcp | | ---------------------------------------------- | ----------------------------------------------- | | "10 + 34 × 341 ÷ 23 = 507.8" ❌ | 514.087 ✅ (math) | | "Here's a UUID: 550e8400-..." 🤷 fake | Cryptographically random UUID v4/v7 ✅ (random) | | "100 days from now is..." 🤔 guess | 2026-05-22 ✅ (date) | | "SHA-256 of password123 is..." 💀 hallucinated | {"hash": "ef92b778bafe..."} ✅ (hash) |

• Deterministic — Same input, same correct output, every time
• Secure — Sandboxed math, ReDoS protection, weak hash warnings
• Private — All computation runs locally, no data sent to external services
• No server config — Install once via npx; MCP client setup required
• No API key — No account or API key required for calc-mcp itself; requires Node.js

Examples

Ask in natural language — your AI assistant selects the appropriate tool.

Math & Numbers

| You ask | You get | Tool | | ---------------------------------------- | ---------- | ---- | | What's 10 + 34 × 341 ÷ 23? | 514.087 | math | | Convert 255 to binary | 11111111 | base | | Is 4539578763621486 a valid card number? | true | luhn |

Text & Encoding

| You ask | You get | Tool | | ------------------------------------------ | -------------------- | ------ | | How many characters in "Hello, World! 🌍"? | 15 chars, 18 bytes | count | | Base64 encode "Hello World" | SGVsbG8gV29ybGQ= | base64 | | Base64 decode "eyJhbGciOiJIUzI1NiJ9" | {"alg":"HS256"} | base64 | | URL-encode "hello world" | hello%20world | encode | | URL-decode "hello%20world" | hello world | encode | | HTML-decode <script> | <script> | encode | | SHA-256 hash of "password123" | {"hash": "ef92b778bafe..."} | hash | | HMAC-SHA256 of "message" with key "secret" | {"hash": "8b5f48702995..."} | hash |

Date & Time

| You ask | You get | Tool | | --------------------------------- | --------------------------- | ---------- | | What time is it in New York? | 2026-02-10T19:00:00-05:00 | datetime | | What's 100 days after 2026-02-11? | 2026-05-22 | date | | When does "30 9 * * 1-5" run? | Mon–Fri at 9:30 | cron_parse |

Generation

| You ask | You get | Tool | | -------------------

... View full README on GitHub