diff --git a/src/main/java/org/opensearch/neuralsearch/processor/NLPProcessor.java b/src/main/java/org/opensearch/neuralsearch/processor/NLPProcessor.java
index 17570190b..7e81c3922 100644
--- a/src/main/java/org/opensearch/neuralsearch/processor/NLPProcessor.java
+++ b/src/main/java/org/opensearch/neuralsearch/processor/NLPProcessor.java
@@ -34,6 +34,8 @@ public abstract class NLPProcessor extends AbstractProcessor {
 
     private final String type;
 
+    // This field is used for nested knn_vector/rank_features field. The value of the field will be used as the
+    // default key for the nested object.
     private final String listTypeNestedMapKey;
 
     protected final String modelId;