spec

Author or review a technical specification — architecture, interfaces, data flow, and the implementation approach engineers will build against, plus the trade-offs behind the choices made. Use when asked to write, update, or review a technical spec or design doc, or to decide how something will be built once what it should do is already settled. Not for defining what a product should do and why, or who it's for — that is prd, which a spec is written against. Not an in-session pre-flight checklist for a single change — see close-the-loop for that.