This is your checklist before you write a single line of SwiftUI or AppKit code. It forces you to identify your app archetype first (document-based, library plus editor, utility, menu bar app, or pro tool), then work through the information architecture, command map, and accessibility plan before building anything. The two core rules are refreshingly direct: prefer system components over custom UI, and if you're customizing bars or chrome, stop and justify it. The Liquid Glass guidance alone (navigation layer yes, content layer no, never stack glass on glass) will save you from common mistakes. Treat the Mac Citizen Checklist and Common Mistakes table as your code review before commit.
npx skills add https://github.com/petekp/agent-skills --skill macos-app-design