Open with the business problem, not a feature list. Who will use it day to day, how many times a day, and how is the job done today? A vendor custom web and saas development who knows what you are trying to achieve often proposes a simpler way to reach it; someone handed only the requirements as given prices the list as written.

Define what is included as concrete flows: what the user does and what the system does in response. Just as important, state explicitly what you are not building. A written out-of-scope list prevents more friction later than almost anything else in the document. Also mark which items are decided and which are still open — honest teams price those differently, and concealing the open questions helps no one.

Write down the hard constraints. This means systems you must integrate with, the data you have and where it lives, compliance requirements, traffic expectations, target platforms and any technology you are committed to. If there is a hard date, say what depends on it: an experienced team will often cut the right scope to hit it, technical consulting services but only if they know it exists.

Say what completion means for each item. Acceptance criteria need not use special syntax: a short list setting out what a user should be able to do will do. This single habit reduces the sign-off process dramatically software maintenance and support services eliminates the usual argument at handover.

One last thing, state what you want in the response. Require a task-level breakdown, the assumptions behind each number, the main risks difference between laravel and ruby on rails a range rather than a single figure. Treat a wide range as information, not evasion: it usually points to where your description is thin. From there rewrite that part and ask for a new estimate — the next version is much more reliable.