Hi!
As far as I see, suppport matrix mentions that ESX is supported as agentless resource (No ULM agent there should be installed)
It means that you can create this resource, using "Netwotk Discovery" and "Agentless Inventory" and then you can perform an agentless monitoring of discovered vmware esx server, using "Monitor Solution" via "Remote Monitoring Server" plug-in (Site Service).
Thanks,
IP.