How can I flag (follow) user by REST API using service resources? I am using flag module to have the following user function. So that the followers will be able to read the blog of the users that they followed.
Now I want to provide api for mobile application, when a userA go to profile of userB, they can follow userB by follow button. Is there any way to return an api by POST method in RESTfull to do like that?
Try the following

Flag 

URL: http://example.com/apiauthd/flag/flag

Method: POST

Parameters:-
    flag_name: like
    action: flag
    uid: { uid of the logged in user}
    entity_id: { uid of the other user to be flagged}


Unflag

URL: http://example.com/apiauthd/flag/flag

Method: POST

Parameters:-
    flag_name: like
    action: unflag
    uid: { uid of the logged in user}
    entity_id: { uid of the other user to be unflagged}