WP REST api.wordpress.org discovery

https://api.wordpress.org is a custom PHP API and is not running WordPress. Thus, there’s no WP REST API that you could use for discovery. That URL has nothing to do with the REST API in core except for that redirect to the handbook.

Unfortunately not all of the API endpoints are documented or either open sourced, as you can see when browsing SVN or looking at the plugins API code directly.

If you have any questions about stuff that’s currently in development there, you should really ask in the #meta Slack channel instead of here or raise an issue on Meta Trac.

Also, since it’s really in development and not intended for public use just yet, I’d highly recommend you to simply stick to the 1.0 or 1.1 version of the API.