SKILL.md and frontmatter
Check required metadata, naming rules, descriptions, Markdown structure, and the conventions agents use to discover a skill.
Free tool
Validate an Agent Skill before you ship it.
Upload a skill package and get spec validation, best-practice lint, package inspection, and an autofix download. No account required.
Live validation totals update after every completed run.
Spec checks
Required frontmatter, naming rules, allowed tool syntax, and package structure are checked before users install the skill.
Best-practice lint
Catch ambiguous descriptions, missing workflows, unresolved references, oversized guidance, and packaging mistakes.
Autofix download
Download a normalized archive when deterministic frontmatter or structure fixes are available, then review the diff before use.
Run the validator
Upload your skill package here.
Your archive is processed for this validation request. No account, trial, or payment details required.
What it validates
Catch broken Agent Skills before an agent tries to use them.
A skill can look reasonable and still fail because its SKILL.md frontmatter is invalid, its package layout is wrong, or an instruction points to a missing file. The free validator checks the whole uploaded package and returns an actionable report.
Complete package structure
Inspect scripts, references, assets, nested paths, and archive layout instead of validating one pasted file in isolation.
Claude Code and Codex skills
Validate portable Agent Skill packages used across agent tools, then optionally export a reviewed skill as a Claude plugin package.
Safe, reviewable autofixes
Preview deterministic fixes and download a normalized archive. The report tells you what changed so validation does not become a blind rewrite.
Agent Skill validator FAQ
Is the Agent Skill validator free?
Yes. You can upload and validate an Agent Skill package without creating an account or choosing a paid plan.
What skill formats can it check?
The validator checks packaged Agent Skills built around SKILL.md, including skills used with Claude Code and OpenAI Codex. Upload a .zip or .tar.gz archive.
Can it fix an invalid skill package?
When deterministic fixes are available, the validator can prepare a normalized archive for download. Review the reported changes before installing or publishing it.