Begin with the problem you are solving, not your preferred technology. Which people will use this, how often, and what does the process look like without it? An estimator who understands the goal can propose an alternative that costs less; someone handed only the requirements as given prices your assumptions along with the work.
Set out the scope as user stories or scenarios: a walk through each important path. Just as important, list what is out of scope. An explicit list of exclusions removes more friction during acceptance than any other single page. Mark too which decisions are settled and which are still open — estimators price uncertainty, and concealing the open questions helps nobody.
List the constraints. This means existing systems the software has to talk to, existing databases and their quality, regulatory obligations, social media marketing agency traffic expectations, which devices matter and stacks you cannot change. If a deadline is real, say why: livewire vs react comparison a team is usually able to rearrange the plan to protect it, but not if the date is a secret.
Define what completion means feature by feature. Clear acceptance criteria do not require special syntax: a short list setting out the expected behaviour is enough. That one addition shortens the review at the end considerably and removes most late-stage disagreement.
To close, say what you expect back. Request an itemised estimate, the assumptions used, the main risks and a range rather than a single figure. Read a wide range as useful information rather than evasion: it tells you where your description is thin. Then clarify that area and ask for a new estimate — the revised figure tends to be the one worth planning around.