diff --git a/specification/webpubsub/data-plane/WebPubSub/preview/2021-05-01-preview/webpubsub.json b/specification/webpubsub/data-plane/WebPubSub/preview/2021-05-01-preview/webpubsub.json
index e74fdeb3e268..9ee358757ed4 100644
--- a/specification/webpubsub/data-plane/WebPubSub/preview/2021-05-01-preview/webpubsub.json
+++ b/specification/webpubsub/data-plane/WebPubSub/preview/2021-05-01-preview/webpubsub.json
@@ -758,7 +758,7 @@
           {
             "in": "query",
             "name": "targetName",
-            "description": "Optional. If not set, grant the permission to all the targets. If set, grant the permission to the specific target. The meaning of the target depends on the specific permission.",
+            "description": "The meaning of the target depends on the specific permission. For joinLeaveGroup and sendToGroup, targetName is a required parameter standing for the group name.",
             "type": "string"
           },
           {
@@ -820,7 +820,7 @@
           {
             "in": "query",
             "name": "targetName",
-            "description": "Optional. If not set, revoke the permission for all targets. If set, revoke the permission for the specific target. The meaning of the target depends on the specific permission.",
+            "description": "The meaning of the target depends on the specific permission. For joinLeaveGroup and sendToGroup, targetName is a required parameter standing for the group name.",
             "type": "string"
           },
           {
@@ -882,7 +882,7 @@
           {
             "in": "query",
             "name": "targetName",
-            "description": "Optional. If not set, get the permission for all targets. If set, get the permission for the specific target. The meaning of the target depends on the specific permission.",
+            "description": "The meaning of the target depends on the specific permission. For joinLeaveGroup and sendToGroup, targetName is a required parameter standing for the group name.",
             "type": "string"
           },
           {