Open with the business problem, not your preferred technology. Who will use the system, how often, and what happens today? An experienced team who knows what you are trying to achieve can propose an alternative that costs less; someone handed only a feature list prices your assumptions along with the work.
Describe the scope as user stories or scenarios: what the user does and what the system does in response. Equally important, state explicitly what is out of scope. An explicit exclusion list removes more friction later than almost anything else in the document. Indicate as well which parts are firm and which are still under discussion — the difference changes the price, and concealing the open questions only hurts you.
Set out your constraints. These include existing systems the custom affiliate tracking software has to talk to, the data you have and where it lives, security and compliance rules, expected load, which devices matter and infrastructure that is already decided. Where a date is genuinely fixed, say why: an experienced team is usually able to cut the right scope to meet it, kubernetes consulting services but not if the date is a secret.
Write down what completion means for the important items. Acceptance criteria do not require special syntax: a short paragraph describing what a user should be able to do will do. That one addition reduces the review at the end dramatically and removes most late-stage disagreement.
Finally, ask for a specific format. Ask for hire offshore flutter developers a breakdown by feature or module, a written list of assumptions, the risks the team sees and a range rather than a single figure. Treat a wide range as information, not evasion: rapid mvp development it normally identifies where your description is thin. From there tighten that section and ask again — the second estimate tends to be much more reliable.