One month ago I started building an open catalog of Claude Code skills. Yesterday it crossed 69,369 indexed SKILL.md files. This post is the engineering story — what I built, what surprised me, and what's free for anyone to use.
If you've never written a Claude Code skill: it's a Markdown file with YAML frontmatter that gives Anthropic's Claude Code agent specialized behavior. Drop it in ~/.claude/skills/<name>/SKILL.md and Claude can invoke it as a slash command. Think of it like a Vim plugin or a VSCode extension, except the contract is "instructions in English" rather than "code in Lua / TypeScript."
The format is brand-new. The official spec doesn't ship a catalog. The awesome-* lists I could find at the time covered maybe 300 hand-picked entries. Meanwhile, GitHub's code search showed thousands of public repos with SKILL.md files in them. The long tail of the ecosystem was completely invisible. That's the gap I set out to close.
The shape of the problem
Here's what I knew going in:
