This is the skill you reach for when a spec feels too big to start or you're not sure what order to build things in. It pushes you into read-only planning mode first, then walks through dependency mapping, vertical slicing (build one complete user flow at a time instead of all database, then all API, then all UI), and writing tasks with acceptance criteria. The core insight is solid: horizontal slicing across layers leads to integration hell, while vertical slices give you working checkpoints. It's opinionated about task sizing (nothing over 5-8 files), includes a plan template, and has good guidance on what's safe to parallelize. Honestly, the discipline of writing acceptance criteria before touching code prevents most of the "I'll refactor this later" disasters.
npx skills add https://github.com/addyosmani/agent-skills --skill planning-and-task-breakdown