Accessibility hint is an additional information user may require to interact with an element. It is similar to an instruction content author want to provide when interacting with a special control. So, the accessibility hint is not required for standard UI controls. They are available as part of the control themselves. When the content authors use custom controls on the app, then an accessibility hint may be required.
How to provide the accessibility hint?
Android:hint attribute supplies the additional hint to the users. The information that the android:hint can be supplied is explained below.
var accessibilityHint: String. The label and the trait are announced first and after a short pause the accessibility hint will be spoken by the accessibility service such as voiceover.
What is a good accessibility hint?
That does not include the label or hint.
That does not say how to interact (double tap to activate) for standard controls.
That includes what happens if user interacts with the control, if it is not self-explanatory with the label.
Add button Adds the item to the basket. In this example Add is the accessibility label, button is the accessibility trait and Adds the item to the basket is the accessibility hint. Since the label (Add) does not say what and where is it adding, the accessibility hint provides the additional information.
Drag me button, Double tap and hold your finger until you hear a click sound, then drag your finger to move. Lift your finger to drop at the target.
In this example drag me is the accessibility label and button is the view / trait. The rest of the content spoken out by the assistive technology is the hint that explains how to drag and drop an item on the screen.
WCAG Success criteria
3.3.2 Labels Or Instructions (Level A)