A simple tool earns trust by making its purpose and limits clear. Describe the task it supports, the inputs it needs and the decisions it leaves to a person.
A fictional time estimator might multiply assumed hours by an hourly rate. That calculation can illustrate labour-cost exposure under stated conditions. It cannot establish recoverable cash savings merely because the multiplication is correct.
Show the assumptions
Keep units, periods and definitions beside the inputs. Explain how missing or invalid values are handled. Provide a worked example a user can check without trusting the interface blindly.
Where a result depends on uncertain inputs, show that uncertainty in the explanation. Avoid presenting a precise-looking number as more certain than its assumptions permit.
Give the user a useful next step
An output should support a decision: gather a missing input, compare an alternative or discuss an exception. Explain when the task needs a more capable system or a suitably qualified person.
Limiting the claim does not weaken the tool. It makes the result easier to interpret correctly. Prefer a modest function that performs its intended job consistently over an impressive collection of features whose outputs nobody can confidently explain. Useful simplicity includes enough context to keep the user from asking the tool to answer a different question.