Validate AI coding assistant skills against the agentskills specification. Works with Claude Code, Claude Desktop/Web, and Cursor. Catch issues before your users do.
Agent Skills are now an open standard adopted by Claude Code, Cursor, and dozens of coding agents. Your skill needs to work everywhere and follow best practices.
SkillCheck validates:
- Does the YAML frontmatter follow the spec?
- Will it trigger when users actually need it?
- Are the instructions clear and unambiguous?
Copy the skill-check folder to your Claude Code skills directory:
cp -r skill-check ~/.claude/skills/Or clone directly:
git clone https://github.com/olgasafonova/SkillCheck-Free.git
cp -r SkillCheck-Free/skill-check ~/.claude/skills/- Open claude.ai or Claude Desktop app
- Create a new Project (or open an existing one)
- Go to Project settings → Custom instructions
- Copy the contents of
skill-check/SKILL.md(everything after the---frontmatter) - Paste into the custom instructions field
No file installation needed - the skill runs directly from your Project instructions.
Copy the rule file to your project's .cursor/rules directory:
mkdir -p .cursor/rules
cp cursor-rules/skill-check.mdc .cursor/rules/Or clone directly:
git clone https://github.com/olgasafonova/SkillCheck-Free.git
mkdir -p .cursor/rules
cp SkillCheck-Free/cursor-rules/skill-check.mdc .cursor/rules/In Claude Code, Claude Desktop/Web, or Cursor, say any of:
- "skillcheck my skill"
- "check skill at path/to/SKILL.md"
- "validate my skills"
## SkillCheck Results: my-awesome-skill
### Summary
- Critical: 1 | Warnings: 2 | Suggestions: 3 | Passed: 44
### Critical Issues
**[1.2-desc-what]** Line 3: Description missing action verb
**Fix**: Start description with Create, Generate, Build, Convert, etc.
### Warnings
**[4.2-ambiguous-term]** Line 47: Vague term "several" found
**Fix**: Specify exact count or range
### Strengths
- Skill includes example section
- Skill documents prerequisites
- Description includes activation triggers
| Check | What It Catches |
|---|---|
| 1.1-name | Invalid name format, reserved words |
| 1.2-desc | Missing or weak description (WHAT verb + WHEN trigger recommended) |
| 1.3-tools | Unknown or deprecated tool formats |
| 1.4-category | Invalid category format |
| 1.9-xml | XML angle brackets in frontmatter (prompt injection risk) |
| 1.9-arg-hints | Missing argument-hint in frontmatter when $ARGUMENTS is used |
| 1.10-readme | README.md inside skill folder (docs belong in SKILL.md) |
| Check | What It Catches |
|---|---|
| 2.1-lines | File too long (500+ lines warning) |
| 2.3-date | Hardcoded dates that will go stale |
| 2.4-empty | Empty sections with no content |
| 2.8-antipattern-format | Anti-pattern sections using prose instead of tables/bullets |
| 2.9-mcp-tool-unqualified | Unqualified MCP tool names missing server prefix |
| Check | What It Catches |
|---|---|
| 3.1-vague | Generic names like "helper", "utils" |
| 3.2-length | Names too short or too long |
| 3.3-single | Single-word names lacking specificity |
| 3.4-gerund | Gerund naming ("writing-helper" instead of verb-noun) |
| Check | What It Catches |
|---|---|
| 4.1-contradiction | Conflicting instructions |
| 4.2-ambiguous | Vague terms like "several", "appropriate" |
| 4.3-output | Output mentioned but no format specified |
| 4.6-wisdom | Generic advice/platitudes instead of actionable instructions |
| 4.7-desc-workflow-steps | Description summarizes workflow steps (causes agents to skip body) |
SkillCheck also recognizes good practices:
| Check | What It Recognizes |
|---|---|
| 8.1 | Has example section |
| 8.2 | Documents error handling or limitations |
| 8.3 | Description includes activation triggers |
| 8.4 | Specifies output format with examples |
| 8.5 | Uses structured instructions (numbered steps) |
| 8.6 | Documents prerequisites |
| 8.7 | Includes negative triggers to prevent over-triggering |
| 8.8 | Uses ${CLAUDE_SKILL_DIR} for portable path references |
| Level | Meaning | Action |
|---|---|---|
| Critical | Skill may not function | Must fix |
| Warning | Best practice violation | Should fix |
| Suggestion | Could be improved | Nice to have |
| Strength | Good practice detected | Keep it up |
| Feature | Free | Pro |
|---|---|---|
| Structure validation | Yes | Yes |
| Body & naming checks | Yes | Yes |
| Semantic consistency | Yes | Yes |
| Quality patterns | Yes | Yes |
| Anti-slop detection | - | Yes |
| Security scanning | - | Yes |
| Token budget analysis | - | Yes |
| WCAG accessibility | - | Yes |
| Enterprise readiness | - | Yes |
| Production readiness | - | Yes |
| Agent Readiness (L0-L3) | - | Yes |
| MCP server integration | - | Yes |
| CI/CD binary | - | Yes |
Get Pro: getskillcheck.com
- Claude Code (or any AI assistant with file Read capability)
- Works on macOS, Linux, Windows
- No dependencies required
SkillCheck Free is itself a skill/rule file. When you say "skillcheck", your AI assistant reads the validation rules and applies them to your target skill. No external API calls, no binaries - just your assistant following instructions.
Found a bug or have a suggestion? Open an issue at github.com/olgasafonova/SkillCheck-Free/issues
- Website: getskillcheck.com
- Specification: agentskills.io
- Pro version: SkillCheck Pro
MIT - see LICENSE
Built by Olga Safonova