GPTel is a very powerful interface for working with LLMs in Emacs. It took me a while to understand that its real value isn't what you get with M-x gptel, which creates a dedicated chat session and buffer, but rather the ability to sling prompts, context, and LLM output around in a native Emacs way. You can add to the context from dired, from a file, from a buffer, you can select from various prescribed system prompts for different functionality, you can prompt from the minibuffer, the kill-ring, the existing buffer, a selection, you can have the responses go to the minibuffer, the kill-ring, a buffer, the echo area -- it's extremely flexible.

I have a little helper function that uses gptel-request that I use while reading Latin texts. It sets the system prompt so the LLM acts as either a Latin to English translator, or with a prefix argument it breaks down the grammatical structure and vocabulary of a sentence for me. It's very cool.