Q: Do I have to have at least one WORK bodypart? No As for your other questions its hard to say what is happening here without seeing your code. But the return of OK means the you intent has been successfully submitted. There are a number of reasons why you may not actually withdraw energy. Another creep may take the last energy from the container, you can cancel your action or submit another withdraw request to overwrite the first. I would recommend you head over to #help on slack, where friendly people will be able to help you.