ratingExplanation

This term is proposed for full integration into Schema.org, pending implementation feedback and adoption from applications and websites.

Thing > Property > ratingExplanation

A short explanation (e.g. one to two sentences) providing background context and other information that led to the conclusion expressed in the rating. This is particularly applicable to ratings associated with "fact check" markup using ClaimReview.
Values expected to be one of these types
Text
Used on these types
Rating

Source

https://github.com/schemaorg/schemaorg/issues/2300