koyomi SKILL.md skillA
koyomi from i2y/ritsu is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add i2y/ritsu/koyomi@git:20261104.5b400fcPins git:20261104.5b400fc in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- i2y/ritsu
- Path
skills/koyomi/SKILL.md- Versions recorded
- 9
- Latest version
- git:20261104.5b400fc, committed Nov 4, 2026
- First version recorded
- Oct 4, 2026
- Size
- 17,266 bytes
- Repository stars
- 3
- License
- Apache-2.0
Write, check and compile koyomi files (`.cal`), the rules of due dates — closing days, payment days, business days and month arithmetic, such as closing on the 20th and paying on the 10th of the next month or on the business day before when that is a holiday — with calendars of closed days read from published tables of holidays, claims checked on every day of a declared range, and code generated for TypeScript, Python, Go, Rust, PostgreSQL and Wasm. Use when payment terms, a deadline or a…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
## When this applies
The job is a **rule of dates**: a date computed from another by closing, adding days, business
days or months, taking a day of a month, and moving off closed days. Payment terms ("closes on the
20th, pays on the 10th of the next month, on the business day before when that day is closed"),
Net 30, a deadline counted in business days, the end of a period under a statute. koyomi writes
it once as a `.cal`, checks it on every input of a range, shows it to the people who read it,
and generates the same function for five languages and a Wasm module.
It does not apply to decisions made from tables of conditions (a fee schedule, an eligibility
test): those are rulec rules. Nor to times of day in a zone with daylight saving time: koyomi
gives dates, and times only at a fixed UTC offset.
The files bundled with this skill are listed in §7. Read them when you need them, not all up
front.
---
# Working with koyomi
Your part is to write the `.cal`, get it past `ritsu koyomi check`, show it to a person, and generate the
code. Two things stay with people:
- **what the terms and the calendar are**: which days are closed, which table of holidays, what a
…Read the whole file at its exact version.
How to install
mdr add i2y/ritsu/koyomi@sha256:badb106994c789c4The line at the top of this page pins the label git:20261104.5b400fc, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_ps3ppn6mtv5thc62)
1 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 9 versions of this file, between Oct 4, 2026 and Nov 4, 2026, about one every 4 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20261104.5b400fc latest | 2026-11-04 | 5b400fc | 17,266 B | A | view · diff |
| git:20261103.1644521 | 2026-11-03 | 1644521 | 16,697 B | A | view · diff |
| git:20261103.4f1202c | 2026-11-03 | 4f1202c | 16,890 B | A | view · diff |
| git:20261103.c9951f1 | 2026-11-03 | c9951f1 | 16,320 B | A | view · diff |
| git:20261029.200ec28 | 2026-10-29 | 200ec28 | 15,914 B | A | view · diff |
| git:20261023.b7ea664 | 2026-10-23 | b7ea664 | 15,168 B | A | view · diff |
| git:20261006.922bf71 | 2026-10-06 | 922bf71 | 14,646 B | A | view · diff |
| git:20261004.634440d | 2026-10-04 | 634440d | 14,385 B | A | view · diff |
| git:20261004.d3273b2 | 2026-10-04 | d3273b2 | 13,724 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (17266 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
i2y/ritsu · 3 stars · license Apache-2.0 · pushed 2026-11-07 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_ps3ppn6mtv5thc62 GET https://markdownregistry.com/api/v1/resolve?ref=i2y/ritsu/koyomi GET https://markdownregistry.com/api/v1/blob/badb106994c789c42bf38802a541d316a5ce581fc21203b2ecf2b66d39b6b849
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.