Iron Law

Check existing tools before installing new ones.

Red Flags

• "I can write tests later" → STOP. Write them now.
• "This change is too small to review" → STOP. Small bugs become P0 incidents.
• "I don't need to check previous cycle insights" → STOP. You will repeat the same mistake.
• "This is good enough" → STOP. Check the checklist.
• "No time to follow every step" → STOP. Skipped steps cost 3x more later.

Discover

Find existing skills first, then search external marketplaces only when needed and safe. Discovery is registry-first: prefer the official/local/verified registry path before broader community search.

When to Use

• The current skills do not cover the task
• A pipeline references a missing capability
• The user wants to browse or install additional skills

Workflow

0. Check built-in capabilities: Before searching, check if the requested capability is already available through built-in tools (Read for PDFs, WebFetch for URLs, Bash for shell tasks, etc.). If built-in tools suffice, report that and skip external search.
1. Scan local skills by name and description.
2. If no strong match, search external sources in priority order (see Source Prioritization). Treat official/local/verified registry sources as the default adoption path.
3. Candidate Inspection: Fetch and read README/SKILL.md for the top 3 candidates. If inspection is blocked (private repo, rate limit): (a) search package name + "review"/"tutorial", (b) check npm page for README, (c) note "inspection blocked" and apply a -1 score penalty. See references/discover-scoring.md for the full workflow.
4. Score candidates on relevance, popularity, recency, dependency weight, and source trust. Show the full weighted breakdown (see references/discover-scoring.md).
5. Apply the Build vs Install threshold. If no candidate scores above 3.0, recommend a custom pipeline instead.
6. Present ranked options with pinned versions and wait for explicit approval.
7. Install only with approval and only when the environment supports it.

Source Prioritization

Priority	Source	Condition	Trust Tier
1	Local skills/ directory	Always	Tier 1 (highest)
2	GitHub repos with SKILL.md	When gh is available	Tier 2
3	npm packages with claude-code keyword	When npm is available	Tier 3
4	General web search	Always available	Tier 4 (lowest)

Trust tier scores: Tier 1 = 5, Tier 2 = 4, Tier 3 = 3, Tier 4 = 2. Bumps apply for verified orgs or scoped packages.

Evaluation Weights

Each criterion is scored 1-5. The weighted sum produces a final score (1.0-5.0).

Criterion	Weight	Scoring Guide
Relevance	30%	5 = exact match, 3 = partial overlap, 1 = tangential
Popularity	20%	5 = 1000+ stars, 3 = 100-999, 1 = <50
Recency	20%	5 = updated within 30 days, 3 = within 6 months, 1 = >1 year stale
Dependencies	15%	5 = zero or minimal, 3 = moderate (5-15), 1 = heavy or native
Source trust	15%	See trust tier mapping above

Thresholds

Score Range	Action
4.0+	Strong recommendation -- install with confidence
3.0-3.9	Viable with caveats -- list limitations
<3.0	Do NOT recommend. Suggest building a custom pipeline instead.

Safety

• Never auto-install. Pin exact versions (see references/discover-scoring.md).
• Postinstall check: Before recommending any npm package, inspect its package.json for preinstall, install, or postinstall scripts. Flag packages with lifecycle scripts and apply a -1 score penalty. Packages with obfuscated or network-calling lifecycle scripts must be rejected entirely.
• Flag heavy or stale packages.
• Degrade gracefully to local-scan-only mode if marketplace tooling is missing.
• Flag repos with no LICENSE file or suspicious content.

Output Format

Return a ranked list AND save results to ${CLAUDE_PLUGIN_DATA}/discovers/{query-slug}.json:

{
  "query": "...",
  "searched_at": "ISO-8601",
  "built_in_check": { "capable": false, "reason": "Read tool handles PDFs up to 20 pages but cannot extract tables" },
  "candidates": [{ "rank": 1, "name": "...", "source": "...", "score": 3.8, "install_cmd": "...", "inspection_notes": "..." }],
  "recommendation": "install|build-custom|use-builtin"
}

Gotchas

• Never invent package names.
• Never recommend a package without checking recency and source.
• Never skip the approval step.
• Never recommend a bare repo URL without a pinned version or commit hash.
• Never rely solely on metadata -- always attempt Candidate Inspection.
• If marketplace CLI does not exist, skip silently and note the gap.
• Never search externally when built-in tools already handle the capability.
• Always persist discover results to JSON for future reference.

Subagents

searcher: { model: haiku, tools: [Bash, WebSearch], constraint: "return only real results; query sources in priority order" }
inspector: { model: sonnet, tools: [Bash, Read], constraint: "fetch and read README/SKILL.md for top 3; verify claims" }
evaluator: { model: sonnet, tools: [Read], constraint: "score consistently; show full breakdown with rationale" }