The Business Analyst is the first persona in the BMAD chain. Its job is to turn an unstructured problem statement into a bounded, reviewable artifact: the one-page PRD. The one-page constraint is deliberate — if you cannot describe the problem, its constraints, its users, and its success criteria on a single page, you haven't understood it well enough to build it.
The BA persona does not estimate effort, write user stories, or make architectural decisions. Its scope is strictly: what problem are we solving, for whom, under what constraints, and how will we know when we've solved it? Every item outside that scope belongs to a later persona. Keeping the BA focused prevents the analysis phase from expanding into planning work before the problem is clear.
In practice, activating the BA persona means loading the relevant context — stakeholder notes, background documents, any prior attempts — and asking the AI to produce a PRD draft. The human reviews and approves it before handing off to the PM. The approval step is not optional; it is the gate between phases. A BA that produces an approved PRD is the only input the PM persona accepts.