Start with the problem you are solving, not a feature list. Which people will use the system, with what frequency, and how is the job done today? A vendor who understands the goal often proposes a cheaper route to it; a team that receives only a list of screens prices your assumptions along with the work.
Set out the scope as short scenarios: a walk through each important path. Just as important, write down what is out of scope. An explicit exclusion list removes more friction during acceptance than the rest of the brief combined. Mark too which decisions are settled and which may still change — honest teams price those differently, and concealing the open questions only hurts you.
Write down the hard constraints. These include existing systems the software development staff augmentation has to talk to, the data you have and vue.js software development where it lives, regulatory obligations, expected load, target platforms and infrastructure that is already decided. Where a date is genuinely fixed, say why: fintech app development an experienced team is usually able to resequence the work to meet it, but only if they know it exists.
Write down what done means for each item. Testable acceptance criteria need not use any formal notation: a short paragraph setting out the expected behaviour is sufficient. That one addition compresses the sign-off process considerably and closes off the most common source of disputes.
Finally, ask for a specific format. Request a task-level breakdown, the assumptions used, the main risks and a range rather than a single figure. Take a broad range as information, not evasion: it usually points to the part of the brief that needs work. From there clarify that area and ask for a new estimate — the second estimate is far closer to reality.