self review

connector/connect/client/jvm/src/main/scala/org/apache/spark/sql/connect/client/SparkConnectClient.scala

@@ -234,11 +234,13 @@ private[sql] class SparkConnectClient(
   }
 
   private[sql] def addTag(tag: String): Unit = {
+    // validation is also done server side, but this will give error earlier.
     ProtoUtils.throwIfInvalidTag(tag)
     tags.get += tag
   }
 
   private[sql] def removeTag(tag: String): Unit = {
+    // validation is also done server side, but this will give error earlier.
     ProtoUtils.throwIfInvalidTag(tag)
     tags.get.remove(tag)
   }

connector/connect/common/src/main/scala/org/apache/spark/sql/connect/common/ProtoUtils.scala

@@ -95,14 +95,14 @@ private[connect] object ProtoUtils {
     // because the Spark Connect job tag is also used as part of SparkContext job tag.
     // See SparkContext.throwIfInvalidTag and ExecuteHolder.tagToSparkJobTag
     if (tag == null) {
-      throw new IllegalArgumentException("Spark Connect execution tag cannot be null.")
+      throw new IllegalArgumentException("Spark Connect tag cannot be null.")
     }
     if (tag.contains(SPARK_JOB_TAGS_SEP)) {
       throw new IllegalArgumentException(
-        s"Spark Connect execution tag cannot contain '$SPARK_JOB_TAGS_SEP'.")
+        s"Spark Connect tag cannot contain '$SPARK_JOB_TAGS_SEP'.")
     }
     if (tag.isEmpty) {
-      throw new IllegalArgumentException("Spark Connect execution tag cannot be an empty string.")
+      throw new IllegalArgumentException("Spark Connect tag cannot be an empty string.")
     }
   }
 }

connector/connect/server/src/main/scala/org/apache/spark/sql/connect/execution/ExecuteResponseObserver.scala

@@ -166,7 +166,7 @@ private[connect] class ExecuteResponseObserver[T](val executeHolder: ExecuteHold
   }
 
   /**
-   * Make sure that response fields that common should be set in every response are populated.
+   * Populate response fields that are common and should be set in every response.
    */
   private def setCommonResponseFields(response: T): T = {
     response match {