It's very good at guessing from function names and context. This is very impressive the first few times, and very frustrating when working with existing codebases, because it assumes the existence of functions based on naming schemes. When those don't exist, you can go ask it to write them, but this is a rabbit hole that leads to more distractions than necessary (oh now we need that function, which needs this one). It starts to feel like too much work.
Often, it will posit the existence of a function that is named slightly differently. This is great for helping you find corners of an API with functionality you didn't know existed, but insanely frustrating when you're just trying to get code working the first time. You end up manually verifying the API calls.
It only works well with codebases that are probably quite well represented in its training data ime. For more obscure ones one is better off just doing it by themselves. Finetuning may be a way to overcome this, though.
Often, it will posit the existence of a function that is named slightly differently. This is great for helping you find corners of an API with functionality you didn't know existed, but insanely frustrating when you're just trying to get code working the first time. You end up manually verifying the API calls.