I think what you mean is that you want the user_data script on server-i to produce some data that is then passed to the user-data script on server-ii. This is already supported, but in a non-obvious way and not using metadata. The way to do it is with a WaitCondition - server-i's user_data script can post some data to the WaitConditionHandle, which server-ii can then retrieve using get_attr on the WaitCondition.