Begin with the problem you are solving, not your preferred technology. What kind of user will use it day to day, how often, and what does the process look like without it? A vendor who grasps the purpose will suggest a simpler way to reach it; a team that receives only the requirements as given can only price your assumptions along with the work.
Set out the scope as short scenarios: what the user does and what the system does in response. Just as important, list what is out of scope. An explicit exclusion list removes more argument later than the rest of the brief combined. Indicate as well which items are decided and which may still change — honest teams price those differently, and concealing the open questions helps nobody.
List the constraints. This means systems you must integrate with, existing databases and their quality, regulatory obligations, user volumes, target platforms and hire senior node.js developers infrastructure that is already decided. If there is a hard date, say why: a team is usually able to cut the right scope to meet it, but only if they know it exists.
Write down what done means for each item. Clear acceptance criteria do not need special syntax: a short paragraph stating what must be true when the feature works will do. That one addition shortens acceptance testing considerably and closes off the most common source of disputes.
One last thing, state what you want in the response. Require an itemised estimate, the assumptions behind each number, software development pricing models whatever the team considers risky and a range rather than a single figure. Read a wide range as useful information rather than evasion: it usually points to the part of the brief that needs work. From there tighten that section and ask for a new estimate — the second estimate will be the one worth planning around.