My experience with this was pretty bad initially. It's clear Epic and other players don't want to be disintermediated and they're going to make things as inconvenient and broken as possible. Par for the course in healthcare. I had much better results simply downloading test results and appointment notes and asking ChatGPT about them in regular chats.
I also had a good experience providing my full genetic sequence (raw data downloaded from sequencing.com) to Claude Code and having it do analysis for me. It downloaded a bunch of bioinformatics tools and did a good job answering my questions.