@magpie-community/tools-calc

Exact arithmetic, unit conversion and date math, as tools magpie offers every agent it connects. Models get arithmetic wrong (0.1 + 0.2, big powers, days between two dates across a DST change), so this gives them a calculator. It needs no network, no key and no dependency.

Install it from magpie's Plugins › Discover, or with:

magpie plugin add @magpie-community/tools-calc
magpie plugin            # lists its tools

magpie serves the tools on its MCP server, /mcp/magpie/tools, to every agent it has connected. Each tool's name starts with the plugin's short name, calc: calc_eval, calc_convert and calc_date (magpie v0.1.1260 or later; earlier versions named them tools-calc_eval when installed from npm).

Tools

eval {expression, places?} evaluates an expression exactly, in fractions, with no floating point.

• Operators: + - * / % ^ (or **), parentheses, and unary minus.
• Numbers: decimals, 1e9, 0x/0b/0o literals, and 1_000.
• Functions: abs floor ceil round trunc min max gcd lcm fact.
• It answers {exact, decimal}, plus rounded: true when the decimal was cut at places (20 by default).

0.1+0.2          → {"exact":"3/10","decimal":"0.3"}
2^128/3          → every digit, exact
1/0              → an error: division by zero

convert {value, from, to, places?} converts a quantity exactly. value can be an expression, such as 3*1024.

| Kind | Units | |---|---| | Data | bit B kB MB GB TB (1000s), KiB MiB GiB TiB (1024s), kb Mb Gb | | Time | ns us ms s min h d wk | | Length | nm um mm cm m km in ft yd mi nmi | | CSS | px pt pc | | Mass | mg g kg t oz lb | | Angle | deg turn grad | | Temperature | C F K |

1 GiB → MB       → {"exact":"16777216/15625","decimal":"1073.741824","unit":"MB"}

date {date?, add?, to?, timeZone?} does date math on the real calendar.

• date is ISO 8601, unix seconds or milliseconds, or now (the default). It answers the ISO time, weekday, ISO week, day of year and unix time.
• add is a duration, such as 3d 4h, -90m, 1y2mo or ISO P1DT2H. Years, months and days count on the calendar, so Jan 31 + 1mo is the last day of February, and a day across a DST change is still a day.
• to is a second date. The answer then also has between, the time from date (after add) to to, in days, hours, minutes, seconds and calendar years, months and days.
• timeZone is an IANA zone, such as Asia/Shanghai. Dates with no offset are read as that zone's wall time, and the answer shows the local time. Without it, they are UTC.

Test

bun test packages/calc

中文：给 magpie 连接的每个 agent 提供精确计算工具：eval 用分数精确计算表达式，convert 换算数据、时间、长度、质量、角度和温度单位，date 按真实日历做日期加减和间隔（支持时区与夏令时）。不联网，不需要 key。