If you're building skills for Claude, this is the spec guide in executable form. It walks you through the full lifecycle: picking a pattern (simple hub, workflow, rules-based, or mixed), writing frontmatter that actually triggers at the right time, structuring reference files so Claude loads them progressively, and validating against the format specification before you ship. The real value is in the decision trees and the quality checklist, which catch the stuff that breaks skills in practice like reference chains, bloated SKILL.md files, and degrees-of-freedom mismatches. Use it when you're authoring a new skill or debugging why Claude isn't picking up your existing one correctly.
npx skills add https://github.com/mblode/agent-skills --skill agent-skills-creator