Open with the reason this software should exist, not a list of screens. What kind of user will use the system, how often, difference between monolith and microservices what does the process look like without it? A vendor who grasps the purpose often proposes a cheaper route to it; a team that receives only a list of screens can only price the list as written.
Describe the scope as short scenarios: a walk through each important path. Every bit as useful, write down what is out of scope. An explicit list of exclusions saves more disagreement later than the rest of the brief combined. Mark too which items are decided and which may still change — estimators price uncertainty, and concealing the open questions helps no one.
Write down the hard constraints. These include existing systems the livewire software has to talk to, existing databases and their quality, regulatory obligations, user volumes, supported browsers or devices and infrastructure that is already decided. If there is a hard date, say why: a team is usually able to rearrange the plan to hit it, provided they hear about it early.
Write down what completion means feature by feature. Clear acceptance criteria do not need formal language: a short list describing what must be true when the feature works is enough. That one addition reduces the sign-off process by a surprising margin and best laravel development company removes most late-stage disagreement.
Finally, state what you want in the response. Ask for an itemised estimate, the assumptions behind each number, whatever the team considers risky and an optimistic and a pessimistic figure. Treat a wide range as useful information rather than evasion: it usually points to exactly which requirement is unclear. Then tighten that section and app aso agency ask again — the second estimate tends to be the one worth planning around.