How are API's discovered?
 

I'm curious how the wiki sites generate their api list. Here's what I've found so far:

• Tools like this one discover functions that are used by the exported interface code.
• Using the in game /api command. Confused why some api's like AbandonQuest aren't discoverable via this method

Is that pretty much how its done or are there other clever ways of discovering functions?

The /api command is relatively new. Anything in that reference is specifically written to show in its own Blizzard addon. (The same as someone creating a wiki page.) Occasionally, new things are added. It will most likely never contain every single function.

The majority of the API can be discovered by exporting the UI itself and reading what Blizzard does with it.

As for that tool you linked, it's a fancy way of organizing the data available from simply running a loop on the ingame _G table. All global objects (functions, tables, strings, numbers, and booleans) of a Lua environment are in there.