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coo-quack

calc-mcp

by coo-quack
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TypeScript
Remote

Calc MCP

npm version CI License: MIT 📖 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

Generate a UUID v7

019c4b54-aad2-7e52-...

random

Generate a readable 20-char password

hT9jZDojX6sHRJt8vaKS

random

Shuffle ["Alice", "Bob", "Charlie"]

["Charlie", "Alice", "Bob"]

random

Conversion

You ask

You get

Tool

100 miles in kilometers?

160.93 km

convert

72°F in Celsius?

22.22°C

convert

Convert #FF5733 to RGB

rgb(255, 87, 51)

color

Convert rgba(255, 0, 0, 0.5) to 8-digit HEX

#ff000080

color

Analysis & Parsing

You ask

You get

Tool

Extract numbers from "abc123def456"

123, 456

regex

Does 1.5.3 satisfy ^1.0.0?

true

semver

Does 1.8.0 satisfy ">=1.5.0 <2.0.0"?

true

semver

IP range of 192.168.1.0/24?

192.168.1.1 – .254 (254 hosts)

ip

Edit distance: "kitten" → "sitting"

3

diff

Unicode info for "€"

U+20AC, Currency Symbols

char_info

Is {"name":"test"} valid JSON?

valid, object

format_validate

Decode & Parse

You ask

You get

Tool

Decode this JWT: eyJhbGci...

{ alg: "HS256", name: "John Doe" }

jwt_decode

Parse https://example.com/search?q=hello

host: example.com, q: "hello"

url_parse

All 21 Tools

Tool

Description

math

Evaluate expressions, statistics

count

Characters (grapheme-aware), words, lines, bytes

datetime

Current time, timezone conversion, UNIX timestamps

random

UUID v4/v7, ULID, passwords (readable, custom charset), random number, shuffle

hash

MD5, SHA-1, SHA-256, SHA-512, CRC32, HMAC

base64

Encode / decode

encode

URL, HTML entity, Unicode escape

date

Diff, add/subtract, weekday, wareki

regex

Test, match, matchAll, replace

base

Number base conversion (2–36)

diff

Line diff, Levenshtein distance

format_validate

Validate JSON, CSV, XML, YAML

cron_parse

Human-readable cron + next runs (weekday/month names supported)

luhn

Validate / generate check digits

ip

IPv4/IPv6 info, CIDR contains check, range calculation

color

HEX ↔ RGB ↔ HSL (alpha channel supported)

convert

8 categories, 146 unit names: length, weight, temperature, area (tsubo, tatami), volume, speed, data, time

char_info

Unicode code point, block, category

jwt_decode

Decode header + payload (no verification)

url_parse

Protocol, host, path, params, hash

semver

Compare, validate, parse, range satisfaction

Install

Claude Code

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

Claude Desktop / Cursor / Windsurf

Add to your config file:

App

Config path

Claude Desktop (macOS)

~/Library/Application Support/Claude/claude_desktop_config.json

Claude Desktop (Windows)

%APPDATA%\Claude\claude_desktop_config.json

Cursor

~/.cursor/mcp.json

Windsurf

~/.codeium/windsurf/mcp_config.json

{
  "mcpServers": {
    "calc-mcp": {
      "command": "npx",
      "args": ["--prefix", "/tmp", "-y", "@coo-quack/calc-mcp@latest"]
    }
  }
}

VS Code (GitHub Copilot)

Add to .vscode/mcp.json in your workspace:

{
  "servers": {
    "calc-mcp": {
      "command": "npx",
      "args": ["--prefix", "/tmp", "-y", "@coo-quack/calc-mcp@latest"]
    }
  }
}

Docker Image

Calc MCP is available as a Docker image from GitHub Container Registry:

docker run --rm -i ghcr.io/coo-quack/calc-mcp:latest

Or use in MCP client config:

{
  "mcpServers": {
    "calc-mcp": {
      "command": "docker",
      "args": ["run", "--rm", "-i", "ghcr.io/coo-quack/calc-mcp:latest"]
    }
  }
}

Available tags:

  • ghcr.io/coo-quack/calc-mcp:latest — Latest release

  • ghcr.io/coo-quack/calc-mcp:X.Y.Z — Specific version (replace X.Y.Z with the desired version)

Other MCP Clients

Calc MCP works with any MCP-compatible client. Run the server via stdio:

npx --prefix /tmp -y @coo-quack/calc-mcp@latest

Point your client's MCP config to the command above. The server communicates over stdio using the standard Model Context Protocol.

Development

bun install
bun run dev       # Start dev server
bun test          # Run tests
bun run lint      # Biome
bun run format    # Biome

Security

calc-mcp processes all data locally and does not:

  • ❌ Send data to external servers

  • ❌ Log data to files or remote services

  • ❌ Store processed data persistently

For detailed security information, see SECURITY.md.

Safe Usage with LLMs

calc-mcp itself is local-only. However, when used via an LLM, your inputs are sent to the LLM provider (Anthropic, OpenAI, etc.).

  • ✅ DO: Use test/sample data when possible

  • ✅ DO: Use local-only LLMs for sensitive operations

  • ❌ DON'T: Pass production secrets to MCP tools (they will be sent to your LLM provider)

Example:

# ❌ Unsafe: Any secret passed to MCP tool is sent to your LLM provider
# Tool: hash
# Input: { "input": "sk-1234567890abcdef", "algorithm": "sha256" }

# ✅ Safe: Use test data only (for learning/development)
# Tool: hash
# Input: { "input": "test-value-123", "algorithm": "sha256" }

# ✅ For production secrets: Use local-only LLMs or process outside MCP

Note: Error messages are automatically sanitized to prevent accidental data leakage.

For security issues, please see our Security Policy.

License

MIT

This server cannot be installed

-
security - not tested
A
license - permissive license
-
quality - not tested

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