APG
Acronymaria authoring practices guide, authoring practices guide, w3c apgDefinition
The ARIA Authoring Practices Guide — the W3C's catalog of how to build accessible interface components, one pattern per component, each giving the roles and attributes to apply, the keyboard interaction to implement, and a working example
Guidance, not specification: WAI-ARIA says what role="tablist" means, and the APG says what a tab list has to do — which key moves between tabs, what aria-selected tracks, where focus goes on activation. That second half is where accessible components are actually won or lost, because ARIA attributes describe and never behave. Its own advice opens with the first rule of ARIA: reach for the native element before the pattern.
The answer to "I know the role, but what is this supposed to do when someone presses the arrow key?"
Avoid: treating a pattern as a component library. The APG gives behavior and a reference example; it ships nothing. Reka UI, which Nuxt UI is built on, is one implementation of that behavior — reading the pattern is how you check whether an implementation is right.