A company wants to ensure that its Retrieval Augmented Generation (RAG) system retrieves all relevant...

The verified answer is B. Recall. In a Retrieval Augmented Generation system, the retrieval component must find the documents or passages that contain the information needed to answer a user query. The question specifically says the company wants to retrieve all relevant documents and avoid missing important information. That wording points directly to recall. Recall measures how many of the relevant items were successfully retrieved out of all relevant items that should have been retrieved. In practical RAG evaluation, high recall means the retriever is less likely to omit important source documents from the context sent to the language model.

Faithfulness is incorrect because it evaluates whether the generated answer is grounded in, and consistent with, the retrieved context. It is a generation-quality metric, not the primary retrieval-coverage metric. A response can be faithful to retrieved context even if the retriever failed to include some important documents. Mean reciprocal rank is incorrect because it measures how highly the first relevant result appears in the ranked list. It is useful for ranking quality, but it does not directly confirm that all relevant documents were retrieved. Precision is incorrect because precision measures how many retrieved documents are actually relevant. High precision reduces irrelevant results, but it can still miss relevant documents if the retriever returns only a narrow subset.

AWS documentation separates retrieval-focused evaluation metrics from response-generation metrics. For knowledge base retrieval-only evaluations, AWS lists built-in retrieval metrics such as context relevance and context coverage, while response generation evaluations include metrics such as faithfulness, correctness, completeness, and helpfulness. This distinction supports the principle that retrieval coverage and not missing relevant information is a retrieval-side concern. In standard information retrieval terminology, the metric that best captures “do not miss relevant documents” is recall.