Who it's for
Developers who use Claude Code, Codex or another coding agent and want to write skills of their own. You need a terminal and one task you repeat, and the four lessons build the same sample skill from start to finish.
Lessons
- 1Skill description: write the name and description so your skill loadsWrite a skill description that agents act on: what the skill does, when to use it, and how to fix a skill that never triggers in Claude Code.
- 2Skill scripts and references: keep SKILL.md short with progressive disclosureSplit a skill into SKILL.md, references, scripts and assets so the agent loads only what a task needs. Covers the layout, size limits and script design.
- 3Test a Claude skill: trigger checks, evals and a no-skill baselineTest an agent skill two ways: trigger checks that show whether it loads, and evals that compare its output with and without the skill. Claude Code steps.
- 4Install Agent Skills in Claude Code, Codex and other agentsInstall an Agent Skill in Claude Code, Codex, Cursor, Gemini CLI or VS Code: the personal and project folders each reads, and plugins to share a skill.
Frequently asked questions
Is the Agent Skills course free?
Yes, all four lessons are free to read.
What do I need before I start?
A coding agent such as Claude Code and a terminal. Lesson 3 also uses jq, and any skill you already have works in place of the sample.
Do the lessons only cover Claude Code?
No. The format is shared, so lesson 4 names the folders Codex, Cursor, Gemini CLI and VS Code read. Most commands and tests use Claude Code, because its documentation gives them.
What is a SKILL.md file?
It is the one required file in a skill's folder: YAML frontmatter with a name and a description, then the instructions in Markdown. Lesson 1 starts from there.