When should you use RAG alone, an agent alone, or both...

The decision splits cleanly along two questions: does the task need actions, and does it need document knowledge.

• RAG alone fits pure question-answering over a knowledge base with no side effects — an internal FAQ bot that only ever needs to surface and summarize existing documents, where low latency and simplicity matter more than flexibility.
• An agent alone fits pure action orchestration where document knowledge isn’t really the bottleneck — a CI/CD pipeline that tests, builds, and deploys code doesn’t need to retrieve anything; it needs to sequence operations correctly.
• Both together (Agentic RAG) fits the common case where a system needs to do both: answer from documents and take actions based on what it finds. A support agent that searches product docs to answer a question, checks order status via a tool, processes a return, and escalates to a human when it’s unsure is doing all three things in one workflow — pure RAG can’t act, and a pure agent with no retrieval strategy has no grounded way to answer the knowledge half of the question.

Most customer-facing production systems land in the third bucket, which is why agentic RAG gets brought up as often as it does — the pure cases are the exception once a system needs to be genuinely useful rather than a narrow demo.