Brigadier's SuggestionsBuilder#suggest(String, Message) can be used to insert a tooltip on the suggestion:
https://github.com/Mojang/brigadier/blob/872658c7372b47a2938f7a836cd33deebf8feb9a/src/main/java/com/mojang/brigadier/suggestion/SuggestionsBuilder.java#L53

Ideally, Cloud should be able to support these on supported platforms.

The goal is this feature: