Building a browser toolbox: how do you explain what a tool can and cannot diagnose?

I build ToolKnit, a collection of browser utilities. One design question keeps coming up: how do you make a quick tool useful without implying it can prove more than it actually can?

For example, our keyboard tester shows the key events that reach the browser. That can help someone compare individual taps or combinations, but a missing event can also come from focus, remapping, the connection, or a system shortcut. It cannot certify the health of a physical switch.

The tool: https://toolknit.com/tools/keyboard-tester.html

I am interested in how other makers communicate limitations at the point of use. Do you prefer a short warning near the result, an expandable explanation, or something else?