Both good answers.
But in these days of increased awareness of Arc Flash dangers, measuring current in the MCC bucket may come with some added procedural requirements for opening the door when live ("Hot Work Permits), as well as added PPE based on the "incident energy" in the MCC as a whole and the fact that an arc blast could start in some area other than where you are working yet still put you in danger. I've heard it argued that opening the motor terminal box while energized does not present the same risk of arc flash danger. I'm not sure I agree 100%, but I do think it is slightly less risky, depending on how the terminations are made up (i.e. bolted connections fully wrapped or covered).
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden