What is an AI Agent? How do you build one with Spring AI?

An agent is an LLM that reasons over a goal, picks tools, executes them, observes results, and repeats (the ReAct loop) until done. In Spring AI: expose multiple @Tool methods and let the LLM orchestrate which to call, add MessageChatMemoryAdvisor for multi-turn state, and optionally use MCP for external tool ecosystems.