Start with the reason this software should exist, not a list of screens. Who will use it day to day, with what frequency, and how is the job done today? A vendor who grasps the purpose can propose a simpler way to reach it; a team that receives only a list of screens can only price the list as written.
Define what is included as short scenarios: a walk through each important path. Just as important, write down what the first release deliberately excludes. A written out-of-scope list saves more disagreement at delivery time than the rest of the brief combined. Mark too which parts are firm and outsource react native development which are still under discussion — honest teams price those differently, and concealing the open questions helps nobody.
List the constraints. This means the platforms and services involved, the data you have and where it lives, regulatory obligations, traffic expectations, web development company russia target platforms and stacks you cannot change. If there is a hard date, say what depends on it: a team is usually able to resequence the work to protect it, but not if the date is a secret.
Say what done means feature by feature. Testable acceptance criteria need not use special syntax: a short list setting out what a user should be able to do is enough. This one section compresses acceptance testing considerably and removes most late-stage disagreement.
To close, say what you expect back. Require an itemised estimate, livewire vs alpine js the assumptions behind each number, whatever the team considers risky and an optimistic and a pessimistic figure. Treat a wide range as a signal about the brief: it tells you where your description is thin. At that point clarify that area and ask for a new estimate — the revised figure will be much more reliable.