Begin with the reason this software should exist, not a list of screens. Who will use it day to day, how often, and what happens today? A vendor who knows what you are trying to achieve often proposes a cheaper route to it; a team that receives only a feature list will price exactly what you asked for.
Define what is included as concrete flows: a walk through each important path. Equally important, write down what the first release deliberately excludes. An explicit list of exclusions prevents more argument at delivery time than any other single page. Indicate as well which items are decided and which are still under discussion — estimators price uncertainty, and pretending everything is fixed helps nobody.
Set out your constraints. This means systems you must integrate with, existing databases and their quality, compliance requirements, traffic expectations, target platforms and infrastructure that is already decided. If a deadline is real, explain what drives it: a good team is usually able to rearrange the plan to hit it, provided they hear about it early.
Write down what done means feature by feature. Clear acceptance criteria do not need special syntax: a short list describing what must be true when the feature works will do. This one section shortens the review at the end by a surprising margin and removes the usual argument at handover.
One last thing, say what you expect back. Require an itemised estimate, a written list of assumptions, custom web application development whatever the team considers risky and a low number and a high number. Take a broad range as a signal about the brief: it tells you the part of the brief that needs work. Then tighten that section and golang web development services request a revised number — the next version will be much more reliable.