Decide between RAG, long-context, structured tool retrieval, and prompt-only approaches for grounding an LLM in private or fresh data. Use when the user is designing a knowledge-grounded agent or chatbot and mentions RAG, vector search, embeddings, retrieval, chunking, long context, context window, tool retrieval, hybrid search, rerank, or asks "do I need RAG?" / "should I just use a big context window?".
