To assist .. here is a link to the earliest archive of the WoW API online so you can see Blizzards api code for the early expansions. Just go forward if you want to look at later versions to prepare potential code changes if Blizzard uses a version in between the original and the current api versions.
Earliest / First WoW api
https://www.townlong-yak.com/framexml/1.1.2
The latest Original Classic WoW api before Burning Crusade expansion
https://www.townlong-yak.com/framexml/1.12.1