Open enterprise software development with java the problem you are solving, not a feature list. Who will use this, how often, and how is the job done today? An experienced team who grasps the purpose often proposes an alternative that costs less; one who only sees the requirements as given can only price your assumptions along with the work.
Define what is included as user stories or scenarios: who does what, and what happens next. Every bit as useful, write down what the first release deliberately excludes. An explicit exclusion list removes more friction later than almost anything else in the document. Mark too which items are decided and which are still open — estimators price uncertainty, and pretending everything is fixed only hurts you.
Write down the hard constraints. The list covers the platforms and flutter development services involved, the data you already hold and its condition, regulatory obligations, traffic expectations, supported browsers or devices and stacks you cannot change. If there is a hard date, say what depends on it: a team is usually able to rearrange the plan to hit it, provided they hear about it early.
Define what done means feature by feature. Clear acceptance criteria need not use any formal notation: a plain-language note describing what a user should be able to do is sufficient. That one addition reduces acceptance testing by a surprising margin and closes off the usual argument at handover.
Finally, say what you expect back. Ask for an itemised estimate, a written list of assumptions, laravel vs node js the risks the team sees and an optimistic and rust development company a pessimistic figure. Treat a wide range as a signal about the brief: it usually points to the part of the brief that needs work. At that point tighten that section and ask again — the next version tends to be the one worth planning around.