diff --git a/google/cloud/dataplex/v1/data_quality.proto b/google/cloud/dataplex/v1/data_quality.proto
index 8f0eb1759f735..bc2d57403c775 100644
--- a/google/cloud/dataplex/v1/data_quality.proto
+++ b/google/cloud/dataplex/v1/data_quality.proto
@@ -108,6 +108,9 @@ message DataQualityResult {
   bool passed = 5;
 
   // A list of results at the dimension level.
+  //
+  // A dimension will have a corresponding `DataQualityDimensionResult` if and
+  // only if there is at least one rule with the 'dimension' field set to it.
   repeated DataQualityDimensionResult dimensions = 2;
 
   // A list of all the rules in a job, and their results.