While LLMs excel at generating cogent text based on their training data, they may also need to interact with external systems. Kiran Prakash describes how we get them to construct external function calls to do this. The LLM does not execute these calls directly, instead it creates a data structure that describes the call, passing that to a separate program for execution and further processing. The LLM's prompt includes details about possible function calls and when they should be used.