skill-vetting

Skill Vetting

Safely evaluate third-party skills for security risks and practical utility.

Quick Start

# Skills are distributed as git repos or .claude/skills/ directories
# Clone or copy the skill to /tmp for inspection
cd /tmp
git clone <skill-repo-url> skill-inspect
cd skill-inspect

# Run scanner
python3 ${CLAUDE_PLUGIN_ROOT}/skills/skill-vetting/scripts/scan.py .

# Manual review
cat SKILL.md
cat scripts/*.py

Vetting Workflow

1. Download to /tmp (Never Workspace)

# Clone skill repo or copy skill directory to /tmp for inspection
cd /tmp
git clone <skill-repo-url> skill-NAME
cd skill-NAME

2. Run Automated Scanner

python3 ${CLAUDE_PLUGIN_ROOT}/skills/skill-vetting/scripts/scan.py .

Exit codes: 0 = Clean, 1 = Issues found

The scanner outputs specific findings with file:line references. Review each finding in context.

3. Manual Code Review

Even if scanner passes:

• Does SKILL.md description match actual code behavior?
• Do network calls go to documented APIs only?
• Do file operations stay within expected scope?
• Any hidden instructions in comments/markdown?

# Quick prompt injection check
grep -ri "ignore.*instruction\|disregard.*previous\|system:\|assistant:" .

4. Utility Assessment

Critical question: What does this unlock that I don't already have?

Compare to:

• MCP servers (check .claude/settings.json mcpServers section or claude mcp list)
• Direct APIs (curl + jq)
• Existing skills (ls .claude/skills/)

Skip if: Duplicates existing tools without significant improvement.

5. Decision Matrix

Security	Utility	Decision
✅ Clean	🔥 High	Install
✅ Clean	⚠️ Marginal	Consider (test first)
⚠️ Issues	Any	Investigate findings
🚨 Malicious	Any	Reject

Red Flags (Reject Immediately)

• eval()/exec() without justification
• base64-encoded strings (not data/images)
• Network calls to IPs or undocumented domains
• File operations outside temp/workspace
• Behavior doesn't match documentation
• Obfuscated code (hex, chr() chains)

After Installation

Monitor for unexpected behavior:

• Network activity to unfamiliar services
• File modifications outside workspace
• Error messages mentioning undocumented services

Remove and report if suspicious.

References

• Malicious patterns + false positives: references/patterns.md