Anatomy of an AI Agent: How Tool Calling Actually Works
Most explanations of AI agents stop at “the LLM decides which tool to use.” That’s the easy part. The hard part is everything around it: how you define tools so the model actually picks the right one, how you handle failures mid-chain, and how you keep a stateless model acting like it has memory.
This post breaks down the core loop that powers every agent we build at Replyant.
The Agent Loop
Every AI agent, regardless of framework, runs the same fundamental cycle: