Backup Plan for Virtual Machines

I am trying to create a backup plan for three VMware virtual servers. I have successfully imported the ESXVirtualAppliance and can connect from the Management Console. But when I try to create a backup plan I receive a warning...

"You are trying to back up a virtual machine with some resitrictions on the backup process. These are the following machines: XXXXXXXX, XXXXXX, XXXXXXX - In the created backup, the virtual machine can be in an inconsistent state, since no integration tools are installed on the virtual machine being backed up."

I can find no mention of any integration tools anywhere. I can still save the backup plan but am I going to get errors?