A useful first release completes one important journey. A long feature list can obscure that journey before the implementation begins.
Name the user and the task
Write down who uses the product, what they need to accomplish and where that action starts and ends. Include the operational steps around the interface.
Make the boundaries explicit
Record what the release includes, what it deliberately leaves for later and which external systems it depends on. Scope is easier to assess when the exclusions are visible.
Agree the acceptance checks
Describe what a reviewer should be able to do with the working product. Include payment failures, permission boundaries and interrupted connections where they affect the journey.
Choose the next milestone
A written scope should lead to a reviewable piece of work. Use that outcome to decide what needs to happen next.