Begin with the problem you are solving, not a feature list. What kind of user will use it day to day, with what frequency, and what happens today? An experienced dedicated development team who understands the goal often proposes an alternative that costs less; one who only sees a list of screens can only price the list as written.
Set out the scope as short scenarios: a walk through each important path. Every bit as useful, list what is out of scope. An explicit list of exclusions removes more argument during acceptance than any other single page. Also mark which items are decided and blockchain consulting services which are still open — estimators price uncertainty, and concealing the open questions only hurts you.
List the constraints. The list covers existing systems the software has to talk to, the data you already hold and its condition, compliance requirements, expected load, which devices matter and any technology you are committed to. Where a date is genuinely fixed, explain what drives it: a good team will often resequence the work to protect it, provided they hear about it early.
Say what the word done means for the important items. Acceptance criteria do not require formal language: application support and maintenance services a plain-language note describing what must be true when the feature works is enough. This one section shortens the sign-off process by a surprising margin and removes the usual argument at handover.
Finally, say what you expect back. Ask for a breakdown by feature or module, the assumptions behind each number, flutter development agency whatever the team considers risky and an optimistic and a pessimistic figure. Take a broad range as information, not evasion: it normally identifies the part of the brief that needs work. From there clarify that area and ask again — the revised figure tends to be much more reliable.