Free SKILL.md Generator and Checker
Agent Skills are the new open standard for teaching AI assistants like Claude new abilities — each skill is a single SKILL.md file. Build one with the form below, or check a file you already wrote. Free, no sign-up, nothing uploaded.
Build a SKILL.md
Save it as SKILL.md in a folder named after the skill. Everything happens in your browser — nothing is uploaded.
Check an existing SKILL.md
What is a skill?
A folder with a SKILL.md inside: a short header saying what the skill does and when to use it, then plain-language instructions. The AI reads the header first and only opens the full instructions when your request matches.
The description does the work
Agents choose skills by the description line alone. Say what it does AND when to use it — “Use when the user needs…” is the phrase that gets your skill picked. The checker above flags descriptions that forget the “when”.
An open standard now
Agent Skills started at Anthropic and the specification has been handed to the Agentic AI Foundation, with skill libraries and plugin marketplaces appearing across tools. Skills you write today are meant to travel between assistants.
Questions
Where does the file go? In a folder named after the skill, as SKILL.md — for example pdf-form-filler/SKILL.md — inside your tool’s skills directory.
What makes a name valid? Lowercase letters, numbers and hyphens, up to 64 characters: pdf-form-filler works, PDF Filler does not. The generator counts and warns as you type.
How long can the description be? Up to 1024 characters. Shorter is fine — two or three clear sentences beat a paragraph.
Want AI tools to understand your website too? That is the sibling format: make a free llms.txt for your site.
✓ Last checked November 2, 2026 — we re-test this tool every week to make sure it still works.