up-5-writing-use-case-specs

Writes or revises one use case specification (docs/use_cases/UC-XXX-name.md) that a stakeholder can validate, an engineer can review against and an AI agent can implement without inventing behavior: goal and trigger, preconditions, a 3 to 9 step main success scenario, alternative flows found in three passes with explicit endings, success and failure postconditions, and numbered business rules with boundary examples. Asks at most five decisive questions, keeps observable behavior concrete and mechanism out, and finishes with an invention pass and a structural lint. Use when the user asks to write, draft, specify, extend or fix a use case, scenario, alternative flow, business rule or acceptance behavior, asks to specify step by step what happens when an actor does something, mentions UC-XXX with a writing request, or wants a spec an agent can implement from. Also covers use cases for APIs, scheduled jobs and events.