To answer my own question, you need to use "Get Clients" (/v1/clients), which returns info for all Avamar clients in the given domain/etc.. The CID is returned in the "id" field. So you could build an array or strip out what you want in a calling script, or to get details for a specific client use filter: name=="vmName"
HI all, I'm reading through the REST API documentation and testing commands via swagger-ui, however pretty much all client commands require knowledge of the client's CID but for the use-case of this application we'd only know the client name, not it's CID. Is there a simple way to pass the client name to REST API and obtain it's CID please?  The only option I'm seeing at the moment is performing a recursive GET Clients on the 1000+ clients in our estate and working out the CID from there. TIA!  
REST API - obtaining the CID for a VM