There's already a "tag" mechanism for edits, right? We already tag all edits from visualeditor, for example. For example, on https://en.wikipedia.org/w/index.php?title=User:Cscott&action=history I can see that the tags "2017 wikitext editor" and "Visual edit" have been applied to some of my most recent edits. I assume bot edits are/could be similarly tagged. And indeed https://en.wikipedia.org/wiki/Special:Tags shows a number of bot-related tags.

This is available via prop=revisions if you just add the tags option to rvprop, eg:
https://en.wikipedia.org/wiki/Special:ApiSandbox#action=query&format=json&prop=revisions&titles=User%3Acscott&rvprop=ids%7Ctimestamp%7Ccomment%7Cuser%7Ctags&rvlimit=1
https://en.wikipedia.org/wiki/Special:ApiSandbox#action=query&format=json&prop=revisions&titles=User%3Acscott&rvprop=ids%7Ctimestamp%7Ccomment%7Cuser%7Ctags&rvlimit=100

We could do that, adding a generic "bot-edit" tag, though it'd be lacking in historical data unless we did some sort of backfill. Also available is doing a second API query to the list=users API for more information about the users obtained from your first API call -- all bots are supposed to be in the bot group. E.g. https://en.wikipedia.org/wiki/Special:ApiSandbox#action=query&format=json&list=users&titles=Talk%3AList%20of%20alternative%20shells%20for%20Windows&formatversion=2&usprop=groups&ususers=SineBot

prop=revisions does already include whether the user is anonymous, as well.

After @cscott suggestion it looks like a good way forward is to use the existing query with prop=revisions passing the extra arguments prop=contributors and pcgroup=bots so we get all the information with one request.

@Dbrant / @cooltey / @Sharvaniharan - thoughts on whether the extra arguments is good enough?

In T317166#8254109, @Jgiannelos wrote:

it looks like a good way forward is to use the existing query with prop=revisions passing the extra arguments prop=contributors and pcgroup=bots so we get all the information with one request.

I'm not sure we can combine the two API calls of prop=revisions and prop=contributors, since these two lists seem to be independent of each other, i.e. there's no guarantee that all the users listed in prop=revisions will appear in the list of contributors, so the call to get contributors must necessarily be made after the call to get revisions.

Looking again at this task, I believe the question may be simplified as follows:

When using the API to retrieve a list of edits to pages on my watchlist (list=watchlist) , I get a list of "edits" that includes the field bot=false/true. It also lets me filter the list by "bot / not bot" edits. If this functionality is available in list=watchlist, could it also be built into prop=revisions?