Definition
Groundedness
Groundedness is whether a response is actually supported by the documents retrieved for it, rather than blended with the model's training data. The book presents RAG as a hallucination control: instruct the agent to answer only from provided context and say so when the answer is absent. Because models quietly mix in prior knowledge, groundedness must be measured continuously with evals, and it appears as a production quality metric.
Explained in
Chapter 9: What Is an Agent?
The moment you give an LLM access to knowledge or tools, it becomes an agent. And that makes all the difference.
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