Yfm

yfm — skill0

Adopt YFM

Use YFM for any markdown an agent, index, or ontology pipeline may scan. Follow the existing dialect if one is already in use (Agent Skills, Obsidian, Jekyll, Hugo, etc.) — the x-cmd default applies only when no other dialect governs.

The x-cmd default: three fields

---
tags: [design, front-matter]
description: One-sentence summary a reader uses to decide whether to open this file.
memo:
  2026-07-31T14:30:00+08:00: Cut aliases; renamed third field to memo.
---

# Title

Body...

• tags — top-level list of slugs [a-z0-9-]. Consumer: the collector for ontology indexing.
• description — top-level string. One sentence. Not the Agent Skills description: (that is a SKILL.md-only requirement, governed by skill0-writer).
• memo: — top-level map, the file's revision log. Keys are ISO 8601 timestamps (YYYY-MM-DDTHH:mm:ss±HH:mm, author's local offset); values are short change-descriptions. Newest first. Omit when no history is worth recording.

Applicable scope

• <project>/.x-cmd/story/ — extends with issue: — see usecase/story.md.
• GitHub issue / PR bodies — extends with repo:, number: — see usecase/git-issue-pr-wiki-markdown-etc.md.
• GitHub README.md — default fields only.

Module

The yfm module is a helper. Three commands:

• x yfm ls [path] — list YFM blocks; defaults to the current directory
• x yfm init [path] — write an x-cmd-default block into each markdown file under the path
• x yfm lint [path] — check that each YFM block is valid YAML and follows the dialect it claims

Reading foreign front matter

The collector ingests many dialects. For the spec the default borrows from, see https://agentskills.io/specification. Per-dialect:

• Agent Skills — metadata: is string→string; top level is closed
• Obsidian — tags / aliases / cssclasses reserved
• Jekyll — list or space-separated
• Hugo — TOML possible; site-configured taxonomy