An idea describes a possibility. A working system changes what someone can do. Getting from one to the other is less about predicting every feature and more about learning what matters before committing to it.
Make the idea testable
Name the person who has the problem, the situation in which it occurs, and what they do today. Then describe the smallest change that would make that situation meaningfully better. If the problem cannot be observed, it will be difficult to know whether a build solved it.
Talk to the people closest to the work and look at the current process. Their examples will challenge assumptions that are easy to miss in a planning document. Capture constraints too: devices, connectivity, existing systems, data sensitivity, and who will maintain the result.
Build the riskiest part first
List the things that must be true for the idea to work. Choose the assumption with the greatest cost if it is wrong, and test it with the least expensive useful experiment. That might be a prototype, a manual service, a technical spike, or a small integration test.
Once the main risks are understood, define a first release around one complete journey. A narrow workflow that works end to end is more informative than a large set of disconnected screens.
Put it into real use
Test with representative users and real operating conditions. Decide in advance what signals matter: completion, time saved, errors avoided, or another result tied to the original problem. Make it easy to report issues and provide a clear route back to the previous process if necessary.
A working system is a starting point for better evidence. Use what people do with it to choose the next improvement, and resist adding complexity that has not earned its place.