Design Rationale

A skill for helping designers speak clearly about their decisions using cognitive science, behavioral psychology, and platform standards as the language — not intuition or preference.

Reference files — read these before generating output:

• data/principles.json — structured principle corpus across three tiers: cognitive/behavioral, platform standards, and applied patterns. Look up by principle id or by moment (Tier 3) — don't read the whole corpus for a single-principle request.
• references/examples.md — real-world precedents organized by moment type (onboarding, navigation, conversion, errors, empty states, offboarding). Stays Markdown — the "don't force it" usage judgment here is load-bearing, not just data.

The Core Job

Most designers know what they decided. Fewer can explain why in a way that holds up when someone pushes back. This skill bridges that gap.