Open with the problem you are solving, not a list of screens. What kind of user will use this, with what frequency, and what happens today? An estimator who grasps the purpose can propose a cheaper route to it; a team that receives only a list of screens will price your assumptions along with the work.
Define what is included as concrete flows: a walk through each important path. Equally important, write down what is out of scope. A written out-of-scope list prevents more argument during acceptance than any other single page. Indicate as well which items are decided and which may still change — estimators price uncertainty, and pretending everything is fixed helps nobody.
List the constraints. These include the platforms and services involved, existing databases and their quality, compliance requirements, expected load, which devices matter and infrastructure that is already decided. If there is a hard date, say why: a outsourcing project team will often rearrange the plan to meet it, but not if the date is a secret.
Define what completion means for the important items. Testable acceptance criteria do not need special syntax: a plain-language note setting out what must be true when the feature works is enough. This one section shortens the review at the end considerably and removes most late-stage disagreement.
To close, state what you want in the response. Request an itemised estimate, a written list of assumptions, whatever the team considers risky and an optimistic and a pessimistic figure. Read a wide range as useful information rather than evasion: it normally identifies the part of the brief that needs work. At that point tighten that section and ask for a new estimate — the next js development company version tends to be far closer to reality.