The new docs has removed API documentation from the old wiki, for versions 16,18,19 and 20, and the only one available is 21.
The path used to be “Asterisk XX Documentation/API Documentation/”, for XX is the version and from here there was docs for AMI, ARI etc. The changes happened between 9 and 10 of august in 2023.
I don`t know if the documentation for 21 is identical and they removed to avoid redundancy, or they want to deprecate the APIs, in either way there should be a notice in the docs.
It wasn’t on purpose. Please raise an issue on the documentation project[1]. This is where issues with documentation should go. I have also notified the person doing documentation, but please for all issues with documentation use the Github project so it can be kept track of.