Faithfulness — measures whether the generated answer is factually grounded
in the provided context (hallucination detection).
Score 1.0 = every claim in the answer is directly supported by the retrieved context.
Score 0.0 = the answer is largely fabricated — major hallucinations not in the context.
When to use: Run faithfulness on every evaluation. It is the single most critical
metric for production RAG pipelines — a high faithfulness score confirms your LLM
is staying within the boundaries of retrieved evidence, not inventing facts.
Common-knowledge exemption: Claims any reasonable person already knows
(e.g. "Water boils at 100°C") do not need to appear in the context and are
not penalised. The metric focuses on domain-specific factual claims.
Score interpretation (5-point scale):
1.0: All claims are explicitly supported — excellent, no hallucination
0.75: One or two minor claims slightly exceed the context, but overall grounded
0.5: Some claims supported; others clearly go beyond what the context states
0.25: Most claims are unsupported or contradicted by the context
0.0: Answer is substantially fabricated — severe hallucination
Uses LLM-as-judge pattern — see arXiv:2306.05685 (RAGAS paper).
Faithfulness — measures whether the generated answer is factually grounded in the provided context (hallucination detection).
Score 1.0 = every claim in the answer is directly supported by the retrieved context. Score 0.0 = the answer is largely fabricated — major hallucinations not in the context.
When to use: Run faithfulness on every evaluation. It is the single most critical metric for production RAG pipelines — a high faithfulness score confirms your LLM is staying within the boundaries of retrieved evidence, not inventing facts.
Common-knowledge exemption: Claims any reasonable person already knows (e.g. "Water boils at 100°C") do not need to appear in the context and are not penalised. The metric focuses on domain-specific factual claims.
Score interpretation (5-point scale):
Uses LLM-as-judge pattern — see arXiv:2306.05685 (RAGAS paper).