skill-check

# SkillCheck (Free) Check skills against Anthropic guidelines and the agentskills specification. This file contains Free tier validation rules. **Want deeper analysis?** [Upgrade to Pro](https://getskillcheck.com) for anti-slop detection, security scanning, token optimization, WCAG compliance, enterprise checks, and Eval Kit (auto-generated test prompts for your skills). ## Prerequisites - Any AI assistant with file Read capability (Claude Code, Cursor, Windsurf, Codex CLI) - Works on any platform (Unix/macOS/Windows) - No special tools required (Read-only) ## How to Check a Skill 1. **Locate**: Find target SKILL.md file(s) 2. **Read**: Load the content 3. **Validate**: Apply each rule section below 4. **Report**: List issues found with severity and fixes --- # Free Tier Validation Rules Apply these checks in order. Each subsection defines patterns to match and issues to flag. ## 1. Frontmatter Structure Every SKILL.md must start with YAML frontmatter between `---` markers. ### Required Fields | Field | Required | Rules | |-------|----------|-------| | `name` | Yes | Lowercase, hyphens only, 1-64 chars, no reserved words | | `description` | Yes | WHAT + WHEN pattern, 1-1024 chars | ### Frontmatter Security **Check 1.9-xml-in-frontmatter** (Critical): Frontmatter values must not contain XML angle brackets (`<` or `>`). Frontmatter appears in Claude's system prompt; angle brackets could enable prompt injection. **Detection**: Scan all frontmatter string values (...