Open with the business problem, not a feature list. Which people will use this, how many times a day, and what does the process look like without it? An experienced team who knows what you are trying to achieve often proposes a simpler way to reach it; someone handed only a list of screens can only price the list as written.
Set out the scope as user stories or scenarios: what the user does and what the system does hire developers in usa response. Equally important, state explicitly what you are not building. A written out-of-scope list removes more friction later than any other single page. Also mark which decisions are settled and which are still open — honest teams price those differently, and concealing the open questions helps nobody.
Set out your constraints. These include the platforms and services involved, the data you already hold and its condition, security and compliance rules, traffic expectations, target platforms and stacks you cannot change. Where a date is genuinely fixed, say why: an experienced team can often rearrange the plan to protect it, cost comparison nearshore vs offshore development but only if they know it exists.
Say what done means for the important items. Testable acceptance criteria do not need any formal notation: a short list stating what must be true when the feature works is enough. This one section compresses acceptance testing by a surprising margin and removes the most common source of disputes.
Finally, ask for a specific format. Ask for a breakdown by feature or module, a written list of assumptions, the risks the team sees and an optimistic and a pessimistic figure. Treat a wide range as useful information rather than evasion: it tells you the part of the brief that needs work. From there clarify that area and ask for a new estimate — the next version will be much more reliable.