Typology is something to be done solely in the mind - a model for reflecting on differences between individuals. It is not to be used, or is to be used very cautiously, for actually typing and explaining people - people don't -actually- fit precisely into one category or another; the model just tries to gives us a boundary for interpreting how people work, e.g. in aiding recognition that there are different ways of viewing things and approaching life which are mutually valid despite seeming contradictory, and we can learn what ways are compatible.
Also, using a secondary typing system (e.g. enneagram) alongside MBTI breaks the God-like hold it can have over people's opinion of others - more option weakens (at least temporarily) how seriously it is taken. MBTI does have potential for helping you understand others, but is habit forming, and leads to stereotyping. The system as a whole is not to be discarded, rather it is to be reinterpreted so as to prevent negative outcomes.