Open with the reason this hire software developers should exist, not a feature list. What kind of user will use this, how many times a day, and how is the job done today? A vendor who understands the goal can propose a cheaper route to it; one who only sees a feature list will price your assumptions along with the work.
Set out the scope as user stories or outsource php development scenarios: a walk through each important path. Just as important, state explicitly what is out of scope. An explicit list of exclusions prevents more argument during acceptance than any other single page. Also mark which decisions are settled and which are still open — the difference changes the price, and pretending everything is fixed only hurts you.
List the constraints. This means the platforms and services involved, existing databases and their quality, regulatory obligations, traffic expectations, target platforms and stacks you cannot change. If there is a hard date, say why: a team is usually able to cut the right scope to protect it, but only if they know it exists.
Define what the word done means for the important items. Acceptance criteria do not require special syntax: a plain-language note setting out the expected behaviour will do. This single habit compresses the review at the end dramatically and removes the most common source of disputes.
One last thing, ask web application development for edtech a specific format. Require a breakdown by feature or module, a written list of assumptions, whatever the team considers risky and an optimistic and a pessimistic figure. Read a wide range as useful information rather than evasion: it usually points to exactly which requirement is unclear. Then rewrite that part and ask for a new estimate — the revised figure is the one worth planning around.