Start with the problem you are solving, not a feature list. Which people will use this, with what frequency, and custom python development how is the job done today? An estimator who grasps the purpose will suggest an alternative that costs less; a team that receives only a feature list can only price the list as written.

Set out the scope as short scenarios: what the user does and what the system does in house team vs outsourcing costs response. Equally important, state explicitly what is out of scope. An explicit list of exclusions prevents more disagreement at delivery time than any other single page. Mark too which items are decided and which are still open — the difference changes the price, and concealing the open questions only hurts you.

Set out your constraints. This means existing systems the software has to talk to, existing databases and their quality, cross platform app development company compliance requirements, user volumes, supported browsers or devices and monolith vs microservices comparison infrastructure that is already decided. If a deadline is real, say why: a team will often resequence the work to protect it, but only if they know it exists.

Say what done means feature by feature. Clear acceptance criteria do not need formal language: a short list stating the expected behaviour will do. This one section compresses acceptance testing by a surprising margin and removes the most common source of disputes.

One last thing, state what you want in the response. Require an itemised estimate, the assumptions used, whatever the team considers risky and an optimistic and a pessimistic figure. Take a broad range as a signal about the brief: it tells you exactly which requirement is unclear. Then rewrite that part and ask for a new estimate — the second estimate tends to be far closer to reality.