Function calling is what OpenAI named the structured-output mechanism that lets an LLM invoke a function. Anthropic calls it tool use, Mistral calls it function calling, Gemini has its own convention. Functionally they are the same primitive. Most agent runtimes normalise across them so you don't have to worry about the difference.
Engineering notes from the Digitorn team. No marketing, no launch announcements, no "10 prompts that will change your life". Just the things we write that we'd want to read.
