What Are Agent Skills? Understanding SKILL.md
6 min read · Updated 2026-06-06
An Agent Skill is a reusable instruction package stored as a SKILL.md file. It contains YAML frontmatter with a name and description, followed by Markdown instructions that teach an AI agent how to perform a specific class of tasks consistently. Skills are supported by Claude Code, Claude.ai, the Claude API, and other Agent Skills–compatible tools.
The anatomy of a SKILL.md file
A skill is a folder with a SKILL.md file at its root. The file begins with YAML frontmatter — at minimum a name (lowercase, hyphen-separated) and a description that states what the skill does and when to use it. After the frontmatter comes Markdown describing the workflow: instructions, steps, inputs, expected output, and any notes.
A skill can also bundle supporting files such as scripts, reference documents, or templates that the agent loads when the skill is active.
Why skills are useful
Skills package know-how so it can be reused. Instead of re-explaining a multi-step process every time, you capture it once as a skill, and the agent follows it consistently. This is especially valuable for repeatable workflows like generating a weekly report, formatting a document type, or following a team's review checklist.
- Reusability — write the process once, run it many times.
- Consistency — the agent follows the same steps each time.
- Shareability — skills are plain files you can version and share.
- Portability — the open format works across compatible tools.
Where to find and create skills
Public repositories host many ready-made skills you can study or adapt; PromptVibe maintains a categorized directory of them in the Skills Library. To build your own from a workflow you already follow, the Skill Generator turns a plain-language description into a structured SKILL.md file.
Frequently Asked Questions
What is the SKILL.md format?
SKILL.md is a Markdown file with YAML frontmatter (name and description) followed by Markdown instructions. It is the core file that defines an Agent Skill.
Which tools support Agent Skills?
Agent Skills are supported by Claude Code, Claude.ai, and the Claude API, and the open format is adopted by a growing set of other agent tools.
Do I need to code to create a skill?
No. A basic skill is just structured Markdown. You can write one by hand or generate one from a workflow description using a tool like the PromptVibe Skill Generator.
Put this into practice
Generate a structured prompt or turn your workflow into a reusable Agent Skill — both free.