Claude Code ships with a small library of built-in skills for common workflows. You don't have to write them - they're there from the first session.

What it does

Skills like /simplify (review and simplify recent code changes), /batch (group similar edits), /debug (enable debug logging), and /fast (shift to faster mode) cover the patterns Anthropic has seen repeat across users. Run / in an interactive session to browse the full list.

When to use it

Quick actions that would otherwise need a paragraph prompt.
First-time users who want to see what Claude Code can do.
Troubleshooting - /debug is often the fastest path to logs.
Inspiration for your own skill library.

Gotchas

Built-in skill names can collide with custom skills. Use plugin namespaces if you ship your own.
Some bundled skills require specific plans or features (Opus, fast mode).
The list evolves between releases. Check the menu after upgrades.

Official docs: https://code.claude.com/docs/en/interactive-mode.md#commands