Calc MCP

Calc MCP

📖 [Documentation](https://coo-quack.github.io/calc-mcp/) — 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 -y @coo-quack/calc-mcp@2.1.5

Or just run it

npx -y @coo-quack/calc-mcp@2.1.5

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

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Why?

• 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

Text & Encoding

Date & Time

Generation

Conversion

Analysis & Parsing

Decode & Parse

All 21 Tools

Install

Claude Code

claude mcp add -s user calc-mcp -- npx -y @coo-quack/calc-mcp@2.1.5

Claude Code plugin

Also available as a plugin from the coo-quack marketplace:

/plugin marketplace add coo-quack/claude-code-marketplace

/plugin install calc-mcp@coo-quack

See the installation guide for details.

Claude Desktop / Cursor / Windsurf

Add to your config file:

{

"mcpServers": { "calc-mcp": { "command": "npx", "args": ["-y", "@coo-quack/calc-mcp@2.1.5"] } } }

VS Code (GitHub Copilot)

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

{

"servers": { "calc-mcp": { "command": "npx", "args": ["-y", "@coo-quack/calc-mcp@2.1.5"] } } }

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 -y @coo-quack/calc-mcp@2.1.5

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](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 s