Begin with the reason this software should exist, not a feature list. Which people will use the system, with what frequency, and what does the process look like without it? An estimator who understands the goal can propose a cheaper route to it; someone handed only a list of screens will price your assumptions along with the work.
Describe the scope as short scenarios: a walk through each important path. Every bit as useful, list what the first release deliberately excludes. A written out-of-scope list prevents more disagreement later than the rest of the brief combined. Indicate as well which parts are firm and which are still open — honest teams price those differently, and pretending everything is fixed helps no one.
Write down the hard constraints. The list covers existing systems the software has to talk how to select a software development company, existing databases and their quality, compliance requirements, user volumes, target platforms and any technology you are committed to. 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.
Define what completion means feature by feature. Acceptance criteria do not need any formal notation: llm development company a short list setting out what must be true when the feature works will do. This single habit shortens the sign-off process dramatically and removes the most common source of disputes.
One last thing, ask for a specific format. Request an itemised estimate, the assumptions behind each number, whatever the team considers risky and a range rather than a single figure. Take a broad range as information, not evasion: it usually points to exactly which requirement is unclear. At that point tighten that section and request a revised number — the next version is much more reliable.