toRustCalcMCP

What it is

A Rust port of calc, Landon Curt Noll's arbitrary-precision calculator, that speaks JSON-RPC 2.0 over stdio as an MCP server. The numeric core is exact rational arithmetic, which is the same model calc uses natively, so results are not floating-point approximations.

What you get

• calc_eval — evaluate an expression; expression is required, with mode (real, frac or int), digits and epsilon as per-call overrides
• calc_config — read or change the session's precision and display settings, including input and output base from 2 to 36
• calc_functions — list the builtins, optionally filtered by substring
• 483 builtin names, with variables, user-defined functions, if/while/for control flow, lists, complex numbers and string operations
• A leading ~ in real-mode output marks a rounded or non-terminating rendering, the same convention calc uses
• The same binary also runs as the rcalc command-line calculator and as a browser REPL

Requirements

Rust 1.75 or later to build; cargo build --release produces toRustCalcMCP, which auto-detects MCP versus CLI mode, and rcalc, which is always the calculator. Start it with toRustCalcMCP --mcp to speak JSON-RPC over stdio. digits defaults to 20 in real mode and accepts up to 10000; the default epsilon is exactly 1/10^20. Licensed LGPL-2.1.

Setup effort

Build from source — git clone https://github.com/carlomagnoglobal/toRustCalcMCP.git

Tools you get

4 tools named in the project's documentation. The README's tools table lists three of the four tools; the fourth, calc_session, which resets or inspects session state, is in the project's tool schema and MCP guide. The calculator's 483 built-in functions are used inside calc_eval expressions, not as separate tools.

Requires

Rust 1.75 or later, with cargo, to build the binary

Where it runs

The documented client runs the server on your machine.