Ask HN: Best Practices for LLM Chatbot that references user account details?

What's the current best practice for including personalized user account details (e.g. for queries like "How much did I spend on this credit card last month?") into a LLM chatbot?

Specifically, assuming the user has already been authenticated properly, how is the user details retrieved, how is the data re-formatted, and how is the data ultimately fed into the LLM? This is a function in many popular banking chatbots, e.g. Bank of America's Erica, but there is scarce information about the actual implementation.