For a product marketing designer, vendor brief is mainly an ownership decision. The page should make clear what this role approves, what it only prepares, and who receives the asset next.
For product marketing designer, keep the vendor brief pass focused on deliverables, technical limits, and review milestones. Make one controlled change at a time and retain enough evidence for another person to repeat the decision.
Specify deliverables, naming, formats, budgets, review milestones, source ownership, and what counts as a chargeable revision. Apply this vendor brief guidance to the actual product marketing designer delivery path.