Start with the business problem, not your preferred technology. Who will use the system, 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 will suggest an alternative that costs less; request a project estimate team that receives only a list of screens will price exactly what you asked for.

Define what is included as user stories or scenarios: who does what, and what happens next. Equally important, list what you are not building. An explicit exclusion list saves more disagreement during acceptance than the rest of the brief combined. Also mark which parts are firm and which are still open — honest teams price those differently, and concealing the open questions only hurts you.

List the constraints. These include the platforms and turnkey software development services involved, the data you have and where it lives, compliance requirements, expected load, which devices matter and stacks you cannot change. If a deadline is real, say what depends on it: a good team will often cut the right scope to meet it, but only if they know it exists.

Say what the word done means for each item. Acceptance criteria need not use formal language: a short list stating what must be true when the feature works will do. That one addition shortens the review at the end considerably and removes the usual argument at handover.

To close, say what you expect back. Ask for an itemised estimate, golang development outsourcing the assumptions used, the risks the team sees and a low number and a high number. Treat a wide range as useful information rather than evasion: it normally identifies the part of the brief that needs work. From there clarify that area and ask again — the revised figure is the one worth planning around.