calculator

Safe arithmetic expression evaluator. Useful for models that hallucinate basic math. The parser is hand-rolled — there is no eval, no Go AST, no string-to-code path.

Usage

native-mcp calculator

No flags, no permissions: it's pure compute, no I/O.

Tools

evaluate

Field	Type	Required	Description
expression	string	yes	Arithmetic expression to evaluate.

Returns the numeric result as text. Integer results are formatted without a decimal point; floats use Go's shortest-round-trip representation.

Grammar

+   -   *   /   %        binary
^   **                    power (right-associative)
+   -                     unary
( ... )                   grouping
1.5e2                     scientific notation

Built-in functions

abs, sqrt, pow(x, y), exp, ln (alias log), log10, log2, sin, cos, tan, floor, ceil, round, min(a, b, ...), max(a, b, ...).

Built-in constants

pi, e, inf, nan.

Examples

Expression	Result
2 + 2	4
(7 - 3) * 5	20
2^10	1024
2^3^2	512 (right-assoc, = 2^9)
sqrt(2)	1.4142135623730951
sin(pi/2)	1
min(1, -3, 4)	-3

Errors

The tool returns an isError: true result for:

• Empty or syntactically invalid expressions
• Division or modulo by zero
• Unknown identifiers or functions
• Wrong arity on a built-in function

Register in Claude Code

claude mcp add native-calc native-mcp calculator