Begin with the business problem, not a feature list. Which people will use the system, symfony vs spring how often, and how ai changes software development is the job done today? An experienced team who knows what you are trying to achieve can propose a simpler way to reach it; a team that receives only a list of screens can only price the list as written.
Describe the scope as short scenarios: a walk through each important path. Just as important, write down what is out of scope. An explicit exclusion list saves more argument later than any other single page. Indicate as well which items are decided and which may still change — the difference changes the price, and pretending everything is fixed helps nobody.
Set out your constraints. These include existing systems the software has to talk to, the data you already hold and its condition, compliance requirements, user volumes, target platforms and infrastructure that is already decided. Where a date is genuinely fixed, say why: an experienced team can often cut the right scope to protect it, provided they hear about it early.
Write down what the word done means for the important items. Testable acceptance criteria do not need any formal notation: a short list stating what must be true when the feature works will do. This single habit compresses the review at the end considerably and eliminates most late-stage disagreement.
Finally, ask for a specific format. Request a task-level breakdown, a written list of assumptions, whatever the team considers risky and an optimistic and a pessimistic figure. 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 tends to be the one worth planning around.