The textbook is there so that the model has something reasonably correct to work with and doesn't make up too much wrong stuff to teach.

For tutoring, I think the approach in https://www.nature.com/articles/s41598-025-97652-6 is promising. (Prompts are included in the supplementary material on the last page: https://static-content.springer.com/esm/art%3A10.1038%2Fs415... ) They start with an existing collection of worked exercises, give the chatbot access to the full solution and then let students interact with it to get a walkthrough or just check their own solution, depending on how much help the student thinks they need.