A skill is a SKILL.md file with YAML frontmatter followed by markdown instructions.
Here's a minimal example for a skill that creates a GitHub issue:
---
name: create-issue
description: Create a GitHub issue from a bug report or task description
argument-hint: "[description]"
---
Write your instructions in plain markdown below the frontmatter. Describe what Claude should do step by step, and reference $ARGUMENTS where the user's input goes.
Save the file to .claude/skills/create-issue/SKILL.md. Run /create-issue fix the login bug and Claude follows your instructions with that argument. I'll use this same pattern throughout the rest of this section.