Nothing to install on your machines or in your clusters: clouds are read through their APIs, disks on a copy inside your account.
An agent is software installed on every machine to report its state. Without an agent, the inventory comes from the cloud APIs and the content of disks from a snapshot mounted elsewhere. The advantage: deployment in hours, no software to maintain on hosts, no load on production.
The six clouds are read through their APIs. For disks and databases, a temporary copy is created inside your account, read on an ephemeral instance, then destroyed. Agentless does not mean read-only: those copies require create and delete permissions, requested separately, which you may refuse.
The online demonstration is open to all, on fictitious data. For an instance on your own accounts, request a demonstration.