For successful API calls that return a status code other then 200 I would just ignore them. There are no API methods that will cause havoc by being called twice

For successful API calls that return a status code other then 200 I would just ignore them. There are no API methods that will cause havoc by being called twice (other then maybe sending a duplicate DM.) For failed API calls that return a 200 status code validate the response. For example if you are getting a user then verify that there is a screen_name and id present. If they are present in the response you are fairly safe to assume the call actually succeeded.