Valididity

Target one creature within range, which must succeed on a Wisdom saving throw. If it fails, you are able to determine the validity of the creature's speech. You cannot read the creature's thoughts or determine its motives, but if anything it speaks aloud is untrue or even if it intentionally hides information in its speech, you know instantly. This spell is magically indiscernible; it cannot be sensed by an Intelligence (Arcana) check, a Detect Magic spell, or any other magical means, and the creature you target has no knowledge that the spell has been cast, even if it succeeds on its Wisdom saving throw.