Kairos Lang MCP server

Kairos

English | 日本語版 README（ドキュメントは日本語が正）

The Japanese documentation is canonical; the spec, the descriptor reference, and the stdlib

guides are fully mirrored in English under en/ (every page links its

counterpart). llms.txt carries the machine-readable overview. Requests and issues

in English are welcome — open an issue.

Kairos is a schedule definition language — a small, composable DSL that defines when things should happen. It goes beyond cron-style patterns: schedules like "3 business days before month-end", "the first business day on or after February 1", or dates derived from the lunisolar calendar are all first-class expressions.

premise US { calendar-system: Gregorian; calendar: NYSE; tz: "America/New_York"; wkst: Sun }

@US
monthEnd |> roll(Preceding, on: bizDay) |> shift(-3, unit: bizDay)   # 3 business days before month-end

cron and iCalendar RRULE can express "N calendar days before month-end", but no existing schedule language lets you write "the Nth business day" inside an expression. The root limitation is not a missing feature — their expressions do not compose: you cannot take the dates one rule derives and feed them into the next rule. Kairos is built around this closure property (every expression is a transformation from a time stream to a time stream), so substitute-holiday derivation, fiscal calendars, the Japanese lunisolar calendar, and the 24 solar terms are all written with the same small operator family.

Highlights

not a "skip / shift" flag bolted onto an external calendar object.

• Business-day arithmetic in the language — roll(Preceding, on: bizDay), shift(-3, unit: bizDay);

written in Kairos (stdlib/); fiscal years, ISO weeks, and the Japanese lunisolar calendar (kyūreki) are ordinary definitions, not built-ins.

• Calendars are user-definable — the Gregorian calendar itself is a transparent standard library

rule from the statutory holiday table alone; the rokuyō (六曜) cycle is derived from lunar months.

• Deriving, not enumerating — Japan's substitute holidays and "citizens' holidays" are derived by

are enumerable; evaluation is reproducible.

• Deterministic and auditable — a definition denotes a set of instants. Missed fires during downtime

(covering) instead of silently degrading.

• Staleness is observable — when calendar data runs out, results carry machine-readable annotations

declarations (week start, roll convention, calendar) are errors, not silent misfires.

• Mistake-proofing as static checks — timezone, granularity, and alignment mismatches, and missing

What an error looks like

Every diagnostic has three parts: operator: what is wrong（how to fix it. where the rule lives）. The text is Japanese (the canonical language); the trailing reference (I3, ADR-38, §3.3) is the spec's own numbering and can be looked up in the English mirror. Three real ones from the reference CLI 1.0.5:

Shortened. The full README is on GitHub.