Validate Skills

If you're publishing skills to the Claude Code marketplace, this validates your SKILL.md files against the agentskills.io spec and catches common mistakes before submission. It checks the obvious stuff like name format and description length, plus Claude-specific best practices like keeping skills under 500 lines and avoiding nested references. Made by Callstack, who clearly got tired of manual review. The validation checklist is well structured with specific rules for both spec compliance and style guidelines. Run it with /validate-skills and you'll get a pass/fail report for each skill in your repo. Saves you from the embarrassment of publishing a skill where the directory name doesn't match the frontmatter.

skills.sh installs: 7.6K
GitHub stars: 1.7K
last updated: Aug 21, 2026

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Install

$ npx -y skills add callstackincubator/agent-skills --skill validate-skills --agent claude-code

Installs into .claude/skills of the current project.

Files

Validate Skills

Validate all skills in skills/ against the agentskills.io spec and Claude Code best practices.

Validation Checklist

For each skill directory, verify:

Spec Compliance (agentskills.io)

Check	Rule
`name` format	1-64 chars, lowercase alphanumeric + hyphens, no leading/trailing/consecutive hyphens
`name` matches directory	Directory name must equal `name` field
`description` length	1-1024 characters, non-empty
Optional fields valid	`license`, `metadata`, `compatibility` if present

Best Practices (Claude Code)

Check	Rule
Description format	Third person, describes what + when to use
Body length	Under 500 lines
Loading is one-level deep	`SKILL.md` is the only progressive-disclosure entry point: every reference file must be reachable from `SKILL.md`. References may cross-link each other for navigation (see note below).
Links are markdown	Use `[text](path)` not bare filenames
No redundancy	Don't repeat description in body
Concise	Only add context Claude doesn't already have