Calc MCP21 tools for things AI is not good at

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

🧮

Precise Math

Evaluate complex expressions and compute statistics using mathjs. Results are always deterministic.

🎲

Cryptographically secure UUIDs, ULIDs, passwords, and shuffling using the platform's crypto API.

📅

Timezone conversion, date arithmetic, and cron parsing with deterministic, accurate results.

🔐

SHA-256, Base64, URL encoding, JWT decoding. Deterministic cryptographic operations.

🌈

8 categories, 146 unit names. Length, weight, temperature, area, volume, speed, data, time. Including Japanese units (tsubo, tatami).

🔍

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

LLMs excel at natural language understanding, but can produce incorrect results for tasks that require precision.

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)

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.
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.