Instead of calling an API, agents can just use functions in a REPL. They can also write new views and improve the program if they run into an issue. Honestly, pretty amazing stuff.
Being able to design a program specifically for the workflow I want is pretty neat. There's some vibeslop jank, but Emacs is a little bit jank too.
Pre-existing (or importable) ELisp functions are kinda similar, just a slightly higher level of user skill.