calculator-mcp-server

One tool for all mathematical operations:

A single tool covering 100% of the server's purpose. Theoperationparameter defaults toevaluate, so the common case is just{ expression: "..." }.

- Evaluate— arithmetic, trigonometry, logarithms, statistics, matrices, complex numbers, unit conversion, combinatorics
- Simplify— reduce algebraic expressions symbolically (e.g.,2x + 3x->5 x). Supports algebraic and trigonometric identities
- Derivative— compute symbolic derivatives (e.g.,3x^2 + 2x + 1->6 x + 2)
- Variable scope viascopeparameter:{ "x": 5, "y": 3 }
- Configurable precision for numeric results
- Blank optionalvariableandprecisionvalues from form-based MCP clients are treated as omitted

- Declarative tool definitions — single file per tool, framework handles registration and validation
- Unified error handling across all tools
- Structured logging with optional OpenTelemetry tracing
- Runs locally (stdio/HTTP) or in Docker

- Hardened math.js v15 instance — dangerous functions disabled, evaluation sandboxed viavm.runInNewContext()with timeout
- No auth required — all operations are read-only and stateless
- Input validation: expression length limits, expression separator rejection (semicolons and newlines), variable name regex enforcement
- Result validation: blocked result types (functions, parsers, result sets), configurable max result size
- Scope sanitization: numeric-only values, prototype pollution prevention (blocked__proto__,constructor, etc.)

A public instance is available athttps://calculator.caseyjhand.com/mcp— no installation required. Point any MCP client at it via Streamable HTTP:

{ "mcpServers": { "calculator-mcp-server": { "type": "streamable-http", "url": "https://calculator.caseyjhand.com/mcp" } } }

Add to your MCP client config (e.g.,claude_desktop_config.json):

- Handlers throw, framework catches — notry/catchin tool logic
- Usectx.logfor logging
- Register new tools and resources insrc/index.ts

Issues and pull requests are welcome. Run checks before submitting:

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