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io.github.cyanheads/calculator-mcp-server

by cyanheads · remote · local (npm) · no sign-in to list tools · v0.5.1 · published by GitHub user cyanheads

Evaluate, simplify, and differentiate mathematical expressions.

Changes · 1
CompareRegistry entry

1 tool: 1 change things.

Scanned Oct 21, 2026

1 check matched something in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http calculator https://calculator.caseyjhand.com/mcp

Findings

Matches of fixed checks, with the text they matched.

1 warn
  • Warncalculate

    The server marks "calculate" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "evaluate": a word for a change.

    What this check looks for

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

1 tool

Changes things 1Claude Code: ask
  • calculateEvaluate math expressions, simplify algebraic expressions, or compute symbolic derivatives.1 finding

    Why it is in this group

    • The description's first verb is "evaluate": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "calculate" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "evaluate": a word for a change.

      What this check looks for
    Description, as the server wrote it
    Evaluate math expressions, simplify algebraic expressions, or compute symbolic derivatives. One expression per call. Supports arithmetic, trigonometry, statistics, matrices, complex numbers, units, and combinatorics.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: false

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 0.5.1. Values in angle brackets are yours to fill in.

claude mcp add --transport http calculator https://calculator.caseyjhand.com/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [],
    "ask": [
      "mcp__calculator__calculate"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as calculator. Review it before you use it.