In 2.0 there are the site_type and site_state fields. On Meta sites these fields give the same information, site_type = meta_site and site_state = linked_meta Instead it would be more useful if ...
Run https://api.stackexchange.com/2.0/sites. programmers.stackexchange.com is not in the response.
For Meta Stack Overflow, the 2.0/sites endpoint returns "main_site" rather than "meta_site". All other site_type for other stackexchange sites return correctly. URL: ...
3D Graphics and Game of Go are both failed beta sites. I would not expect them to show up in the /sites list - but they do. Indeed, attempting to list questions on one of the sites fails: ...