WHAT IT IS
Agents differ from chatbots in two ways: they have tool access (search, code execution, APIs, file systems, databases) and they operate in a loop — reasoning about state, taking an action, checking the outcome, and deciding the next step. The pattern is formalized in frameworks like ReAct (Reason + Act) and in agentic runtimes such as the OpenAI Assistants API, Anthropic's tool-use pattern, LangGraph, and CrewAI.
HOW IT WORKS
A well-built agent defines a clear objective, a bounded tool set, an explicit stop condition, guardrails for irreversible actions, and logging/evaluation so regressions are visible. Retrieval-Augmented Generation (RAG) is often a component, not the whole system.
WHEN TO USE
Use agents where work involves multi-step tool use, long context, or decisions that benefit from iteration. Avoid them for simple Q&A a single retrieval call would answer cheaper and faster.