Add external skill

Keep .claude-plugin/marketplace.json and the README Available skills catalog in sync with upstream external skills.

Arguments: $ARGUMENTS

• <owner/repo> [path] [name] → add mode (default).
• update (optionally update <owner/repo> to scope to one repo) → update mode.

Each entry pins a sha Renovate bumps automatically. Plugin name unique across the whole marketplace. Default: one entry per SKILL.md, name = skill folder basename. Exception: a cohesive upstream plugin (has its own .claude-plugin/plugin.json, bundling skills and/or subagents) becomes a single whole-plugin entry whose path is the plugin root — installing it brings every artifact (skills + subagents), name = the name in its plugin.json. See api-scaffolding / shell-scripting.

Discover the skills in a repo with one call (reused by both modes):

curl -fsSL "https://api.github.com/repos/<owner>/<repo>/git/trees/main?recursive=1" \
  | jq -r '.tree[] | select(.path | endswith("/SKILL.md")) | .path | sub("/SKILL.md$";"")'

Fetch the current branch HEAD SHA (shared by all entries from a repo):

curl -fsSL "https://api.github.com/repos/<owner>/<repo>/commits/main" \
  -H "Accept: application/vnd.github.sha"

Fetch a skill's upstream description (a concise one-liner — usually the frontmatter's first sentence): it is stored verbatim in marketplace.json and rendered as-is into the README row.

curl -fsSL "https://raw.githubusercontent.com/<owner>/<repo>/<sha>/<path>/SKILL.md"

If curl is blocked/redirected here, fetch the same URLs via any HTTP tool — the endpoints are identical.

Add mode

1. Parse args. If owner/repo missing, ask for it.
2. Decide granularity. path points at a plugin root (has .claude-plugin/plugin.json) and you want its subagents too → one whole-plugin entry at that root; skip per-skill discovery, take name from the plugin.json. Otherwise discover skills: path = a skill folder → single entry; a parent folder → only folders under it (empty → stop, report); omitted → all (batch).
3. Fetch the SHA.
4. name = arg (single) or folder basename (batch). Confirm every name is free in marketplace.json — report collisions and ask before proceeding.
5. For each skill, fetch its upstream frontmatter description (see the fetch above — a concise one-liner, usually the frontmatter's first sentence). Append each entry to the plugins array (match existing formatting exactly):

   {
     "name": "<name>",
     "source": {
       "source": "git-subdir",
       "url": "https://github.com/<owner>/<repo>",
       "path": "<path>",
       "ref": "main",
       "sha": "<sha>"
     },
     "description": "<concise one-liner from the upstream description, stating what the skill does>"
   }
   

   Never emit a generic placeholder like <owner>/<repo> — <name>: the description must say what the skill does. If the upstream description is empty or unusable, write a one-line summary from the SKILL.md body instead. For a whole-plugin entry, list its bundled artifacts (agents + skills), e.g. "…: bash-pro and posix-shell-pro agents plus the bash-defensive-patterns, bats-testing-patterns, and shellcheck-configuration skills.".
6. Regenerate the README (see below), then validate.

Update mode

For each git-subdir source repo in marketplace.json (or the one named):

1. Discover the repo's current skill folders and fetch its latest SHA.
2. Reconcile against the existing entries:
   • New upstream folder (no entry) → add an entry (as in add mode).
   • Removed upstream (entry whose path no longer has SKILL.md) → list it, ask to confirm, then delete the entry.
   • Bump each surviving entry's sha to the latest (Renovate also does this; harmless to set now).
   • Refresh each entry's description from upstream (a concise one-liner, usually the SKILL.md frontmatter's first sentence — the fetch above). marketplace.json is the source of truth, so this is what the README shows.
3. Regenerate the README, then validate.

Regenerate the README

The README Available skills catalog is a projection of marketplace.json produced by scripts/gen-readme.js — never hand-edit it. It rewrites the section between the <!-- catalog:start --> / <!-- catalog:end --> markers; skill names, descriptions and URLs come from marketplace.json, and the Modes table is derived from the local mode-router plugin's dependencies.

• If you referenced a skill from a new source repo, add a group to scripts/catalog-meta.json (ordered list):

  { "repo": "<owner>/<repo>", "tagline": "<short label>", "kind": "skill" }
  

  Use "kind": "plugin" for a whole-plugin entry (renders a "What it bundles" column). The generator throws if any git-subdir entry's repo has no group (or is not omitted / a mode-router dependency), so this can't be silently missed.
• Run the generator:

  node scripts/gen-readme.js
  

Finish

node scripts/gen-readme.js --check   # README catalog is in sync with marketplace.json
claude plugin validate .

Report what changed (added / removed / description updates). Do not commit — leave that to the user.