Groundedness

Groundedness, also called faithfulness, asks a precise question: of all the statements in this answer, how many are supported by the retrieved source material? You measure it by breaking the answer into individual claims and checking each one. The score is supported claims divided by total claims.

It matters because a fluent answer can still be wrong, and whole-answer quality scores tend to miss that. Checking at the level of each claim is the measure that reliably tracks whether an answer is genuinely backed by its sources.