This is the pre-implementation design layer: colour palettes, typography scales, design tokens, and visual direction before you write any Tailwind. It splits into product UI (dashboards, admin panels, data tables) and marketing (landing pages, brand sites), with separate guidance for each. The marketing track includes CRO psychology, A/B testing methodology, social proof patterns, and conversion benchmarks. Use it when someone says "make this look premium" or "pick a visual style" or you're starting a design system from scratch. Once you have a spec or token set, hand off to the ui skill for actual markup. The boundary is clear: this outputs decisions and direction, ui outputs components and Tailwind classes.
npx skills add https://github.com/mblode/agent-skills --skill ui-design