Open with the problem you are solving, not a feature list. What kind of user will use the system, how many times a day, and what is langchain rag happens today? A vendor who knows what you are trying to achieve will suggest a simpler way to reach it; someone handed only a feature list can only price the list as written.
Set out the scope as user stories or scenarios: a walk through each important path. Equally important, application support services state explicitly what you are not building. A written out-of-scope list removes more argument during acceptance than the rest of the brief combined. Indicate as well which parts are firm and which are still open — honest dedicated teams web development price those differently, and hiding it helps nobody.
List the constraints. This means systems you must integrate with, the data you have and where it lives, security and compliance rules, expected load, supported browsers or devices and stacks you cannot change. Where a date is genuinely fixed, explain what drives it: an experienced team is usually able to rearrange the plan to meet it, but not if the date is a secret.
Write down what done means for the important items. Clear acceptance criteria do not need any formal notation: a short paragraph setting out the expected behaviour will do. This single habit shortens the review at the end dramatically and closes off the usual argument at handover.
One last thing, say what you expect back. Ask for a task-level breakdown, the assumptions behind each number, the risks the team sees and a range rather than a single figure. Read a wide range as information, not evasion: it usually points to exactly which requirement is unclear. At that point tighten that section and ask again — the revised figure is far closer to reality.
