Start with the problem you are solving, not a feature list. What kind of user will use this, with what frequency, and hire mobile app developers what happens today? An estimator who knows what you are trying to achieve will suggest an alternative that costs less; someone handed only a list of screens can only price exactly what you asked for.

Define what is included as short scenarios: a walk through each important path. Equally important, write down what is out of scope. An explicit list of exclusions removes more friction at delivery time than the rest of the brief combined. Indicate as well which items are decided and which may still change — the difference changes the price, and pretending everything is fixed only hurts you.

List the constraints. These include existing systems the software has to talk to, php vs java spring the data you have and where it lives, security and compliance rules, user volumes, vue js vs angularjs target platforms and stacks you cannot change. If a deadline is real, explain what drives it: a team can often cut the right scope to protect it, but only if they know it exists.

Say what completion means for the important items. Testable acceptance criteria need not use any formal notation: a plain-language note setting out what must be true when the feature works is enough. This single habit shortens acceptance testing dramatically and eliminates the most common source of disputes.

To close, state what you want in the response. Require a task-level breakdown, the assumptions used, node.js development outsourcing whatever the team considers risky and a low number and a high number. Read a wide range as a signal about the brief: it normally identifies exactly which requirement is unclear. Then rewrite that part and ask again — the revised figure will be far closer to reality.