I like sequence diagrams and state diagrams (well just straight finite state automata). They bring an extra layer of description that is otherwise very hard to

I like sequence diagrams and state diagrams (well just straight finite state automata). They bring an extra layer of description that is otherwise very hard to extract from the code. I draw them with Plantuml. Text input is really a must have for me. On crowded diagrams it may be difficult to fine-tune the layout though. I still sometimes do class diagrams, although I do not find they carry much info compared to the code. The meaning of arrows is ambiguous and they're too verbose. APIs are better documented with e.g. Doxygen.