Mgmt: Have you documented this user story?
Me: Hm, they say it's done but don't actually say what they did. I'll ask Dev.
Me: Dev, can you tell me what you did to resolve $story?
Dev: I resolved it.
Me: By doing what?
Dev: ????
Me: Just tell me the API endpoint you added.
Dev: ????????? I don't understand.
Me: You said *in your notes* that you added an endpoint for this. What is the endpoint?
Dev: ????? I do not understand your question.

I cannot fix this. It's a damned brick wall.