Comment by DebtDeflation

And the LangChain definition is a further simplification of Anthropic's:

"An AI agent is a system that uses an LLM to decide the control flow of an application."

What gets left unsaid is whether current SOTA LLMs actually have the reasoning and planning capabilities to do this reliably. I would argue that except for code debugging tasks and simple research tasks (iterative Googling with a web browser and then formatting the results into a report format) they do not. That may change in 6 months, but right now the hype has gotten ahead of the capability.