I have the
access_token after authentication from the user. At this point I don't know with which sites this user has registered. Is it possible to get user information like the display name or profile picture from here?
If you need more details about a user on a give site, then turn around and hit
As for display names and profile images, you will have to make at least one call to a site specific method; I typically advise consumers to only query the user's top account (by rep) for that information, it's the same on all sites for > 90% of users with multiple accounts (and > 50% of users only have accounts on a single site). However, if you intend to display all of a user's accounts you will have to make multiple requests.