Begin with the business problem, not your preferred technology. What kind of user will use the system, how often, and how is the job done today? An experienced team who grasps the purpose often proposes a simpler way to reach it; a team that receives only a list of screens prices exactly what you asked for.
Define what is included as user stories or scenarios: what the user does and what the system does in response. Every bit as useful, state explicitly what you are not building. An explicit exclusion list saves more disagreement at delivery time than the rest of the brief combined. Also mark which parts are firm and which may still change — the difference changes the price, and ai automation agency pretending everything is fixed only hurts you.
List the constraints. The list covers systems you must integrate with, the data you have and where it lives, compliance requirements, user volumes, target platforms and any technology you are committed to. If there is a hard date, say what depends on it: a team can often cut the right scope to protect it, provided they hear about it early.
Say what the word done means for each item. Acceptance criteria need not use formal language: python development services a plain-language note stating the expected behaviour is enough. That one addition shortens the review at the end considerably and eliminates the most common source of disputes.
Finally, state what you want in the response. Ask for an itemised estimate, the assumptions used, the risks the team sees and a low number and a high number. Read a wide range as useful information rather than evasion: it tells you the part of the brief that needs work. From there rewrite that part and ask again — the next version tends to be far closer to reality.