Describe the moment, not the feature list
Start with a situation you recognise: a repeated calculation, a document you keep recreating, or a small piece of information that is difficult to find. Write down who is doing the task, what they are trying to finish, and what gets in the way. “A person needs to compare two options without opening a spreadsheet” gives you more direction than “a productivity app.”
Give the first version one job
Write a single sentence that describes the outcome. Then list the minimum inputs and the smallest useful output. A tool that converts a measurement may need a number, two units and a clear result. Accounts, dashboards and reminders can wait unless the task truly depends on them. Simplicity should reduce effort for the person using the tool, even when that requires more care behind the scenes.
Make a rough version people can understand
Before a polished interface, try a sketch, a paper worksheet or a basic working screen. Show the starting point, the action and the result. Use ordinary language for labels. Include an empty state and one example of an invalid input: these often reveal missing decisions sooner than another feature does.
Watch the task, not just the reaction
Ask someone to complete the task without explaining every step. Notice where they pause, what they expect to happen and whether they can tell when they are finished. A friendly “looks great” is encouraging, but it does not tell you whether the tool saves effort. Keep a short list of the obstacles you observed and improve those first.
Decide what would make it worth keeping
Choose a modest measure that matches the purpose: fewer steps, fewer mistakes, a clearer result or a task completed without help. Compare it with the existing way of doing the work. If the rough version does not improve the experience, change the idea before adding more polish.
A small brief to try
Complete these five lines: The person is… / They need to… / Today they struggle with… / The first version will… / We will know it helps when… . Keep the brief beside the prototype. When a new feature appears, ask whether it supports that original promise.