diff --git a/src/core/etl/src/Flow/ETL/RandomValueGenerator.php b/src/core/etl/src/Flow/ETL/RandomValueGenerator.php
index 9769bfc4b..0275cbf7d 100644
--- a/src/core/etl/src/Flow/ETL/RandomValueGenerator.php
+++ b/src/core/etl/src/Flow/ETL/RandomValueGenerator.php
@@ -4,6 +4,9 @@
 
 namespace Flow\ETL;
 
+/**
+ * Random value generator interface for producing random integers and strings.
+ */
 interface RandomValueGenerator
 {
     public function int(int $min, int $max) : int;