Open with the reason this software should exist, not your preferred technology. What kind of user will use the system, with what frequency, and symfony development outsourcing how to choose the right software development partner is the job done today? An experienced team who grasps the purpose often proposes an alternative that costs less; a team that receives only the requirements as given prices exactly what you asked for.
Set out the scope as short scenarios: what the user does and what the system does in response. Equally important, write down what the first release deliberately excludes. An explicit list of exclusions saves more argument later than almost anything else in the document. Also mark which parts are firm and which are still open — honest teams price those differently, and hiding it only hurts you.
Write down the hard constraints. This means existing systems the software has to talk to, existing databases and their quality, security and compliance rules, traffic expectations, supported browsers or devices and infrastructure that is already decided. If a deadline is real, explain what drives it: a good team can often rearrange the plan to protect it, but only if they know it exists.
Say what the word done means for the important items. Testable acceptance criteria need not use any formal notation: livewire vs react a short list describing what must be true when the feature works is sufficient. That one addition reduces the sign-off process dramatically and eliminates most late-stage disagreement.
Finally, ask for a specific format. Request an itemised estimate, the assumptions used, the risks the team sees and a range rather than a single figure. Read a wide range as a signal about the brief: it normally identifies the part of the brief that needs work. At that point tighten that section and request a revised number — the next version tends to be much more reliable.