# Skill Migration Guide — add a root `SKILL.md` (hybrid pattern)

One page. How to make an existing dual-platform skill **natively loadable** as an Agent
Skill without rewriting it. Reference implementations: `custom-skills/16-seo-schema-validator`
and `custom-skills/17-seo-schema-generator`.

## Why

Claude Code / Desktop / API natively load the **Agent Skills format**: a directory whose
**root** holds a `SKILL.md` (YAML frontmatter + body) plus optional bundled resources. Our
older skills keep the directive in `desktop/SKILL.md` and `code/CLAUDE.md` — not at the
root — so they aren't directly loadable. The fix is **additive**: promote a `SKILL.md` to
the root. Keep `code/` and `desktop/` as-is. **No rewrite, no logic change.**

## Target (hybrid) structure

```
XX-skill-name/
├── SKILL.md            # ← NEW: root directive, official format (loadable)
├── scripts/            # ← runnable scripts (single source of truth)
├── references/         # ← heavy docs, loaded on demand
├── templates/          # ← optional
├── fixtures/           # ← optional (sample/test inputs)
├── code/               # KEPT — code/CLAUDE.md redirects to ../SKILL.md + ../scripts
└── desktop/            # KEPT — desktop/SKILL.md + skill.yaml + tools/
```

Scripts live **once** at the root `scripts/`; `code/CLAUDE.md` points to `../scripts/`
(don't duplicate). Don't move existing scripts that other skills already reference.

## Recipe (≈10 min/skill)

1. **Copy** `desktop/SKILL.md` → root `SKILL.md`. (It's already frontmatter + body — the
   right shape; it was just in the wrong place.)
2. **Fix the frontmatter** against the checklist below.
3. **Promote resources** to root siblings: if real scripts/docs live under `code/`, move
   the canonical copy to root `scripts/` + `references/`; reference them from `SKILL.md`
   with **relative paths** (`scripts/foo.py`, `references/bar.md`).
4. **Redirect `code/CLAUDE.md`** to a short pointer: "canonical = `../SKILL.md`; scripts =
   `../scripts/`" (see 16/17 `code/CLAUDE.md`).
5. **Leave `desktop/`** intact (SKILL.md, skill.yaml, tools/). It stays the Desktop view.
6. **Verify** (below). Commit.

## Frontmatter checklist (the only hard requirement)

```yaml
---
name: skill-name-kebab-case        # letters, numbers, hyphens ONLY
description: |                     # third person; START with "Use when…" / what+when
  What it does in one line. Triggers: kw1, kw2, 한국어 트리거.
---
```

- [ ] `name`: kebab-case, no spaces/parens/special chars. (May keep the `NN-` prefix.)
- [ ] `description`: third-person; says **when to use** + trigger keywords (EN + KO).
- [ ] **Whole frontmatter ≤ 1024 characters.**
- [ ] Body: concise markdown (aim < 500 words of always-on content); push detail into
      `references/` and link it — don't `@`-include (that force-loads and burns context).
- [ ] Optional fields allowed: `version`, `author`, `license`, `allowed-tools`, `metadata`.

## Verify before committing

```bash
# frontmatter present + size sane
head -20 custom-skills/XX-skill/SKILL.md
python3 - <<'PY'
import re,sys,pathlib
t=pathlib.Path("custom-skills/XX-skill/SKILL.md").read_text()
m=re.match(r'^---\n(.*?)\n---',t,re.S); assert m,"no frontmatter"
fm=m.group(1); assert len(fm)<=1024,f"frontmatter {len(fm)} >1024"
assert re.search(r'^name:\s*[a-z0-9-]+\s*$',fm,re.M),"name must be kebab-case"
assert 'description:' in fm,"description required"
print("OK: frontmatter valid")
PY
# every relative path referenced in SKILL.md must exist
grep -oE '`(scripts|references|templates|fixtures)/[^`]+`' custom-skills/XX-skill/SKILL.md
# if the skill has scripts, run its bundled sample/fixture end to end
```

## Adopt going forward

- **New skills:** create a root `SKILL.md` from day one (the hybrid above). `code/` +
  `desktop/` remain optional packaging, not the primary directive.
- **Existing skills:** migrate **incrementally** — when you next touch a skill, apply the
  recipe. A bulk migration of all skills isn't worth the churn unless you specifically
  need them all loadable at once.
- When in doubt, copy the shape of `16-seo-schema-validator` / `17-seo-schema-generator`.