diff --git a/dockerimg/createdockerfile.go b/dockerimg/createdockerfile.go
index a5a2c4b..d76dc0b 100644
--- a/dockerimg/createdockerfile.go
+++ b/dockerimg/createdockerfile.go
@@ -211,7 +211,7 @@
   "properties": {
     "extra_cmds": {
       "type": "string",
-      "description": "Extra commands to add to the dockerfile."
+      "description": "Extra dockerfile commands to add to the dockerfile. Each command should start with RUN."
     }
   }
 }`),