A useful website brief begins with the business outcome. Explain who the visitors are, what they need to learn and the action you want them to take. List the current site, the pages that already perform well and any content that must be migrated.
Map the user journey
Describe the main visitor groups and their questions. A prospective client may need service details, proof, pricing guidance and a direct way to contact or buy. The page structure should make those paths easy on both desktop and mobile.
Define the working scope
Include the expected page types, content ownership, forms, language needs, integrations, analytics, accessibility, hosting and maintenance. Note which assets already exist and which must be produced. For an e-commerce site, add products, tax, payments, order emails, fulfilment and refund decisions.
Plan acceptance
Agree what will be tested before launch: responsive layouts, form delivery, checkout, redirects, accessibility, speed, security and editor training. Set out who signs off copy, visuals and the final release. A proposal can then state deliverables, exclusions and milestones against the same brief.
If the requirements are uncertain, a discovery sprint or prototype can help define them before a full build.