Solved! SEE THE SOLUTION
"Cluster-peer-health-get-iter" will report the health status of the peer relationship between this cluster and the other clusters it is peered with (peering is a pre-requisite to SnapMirror replication).
In the past I've used cluster_node_get_iter to query cluster-node-info.
There are a number of fields you can query to get what you want such as is-node-healthy, is-node-epsilon and is-node-eligible.
I generally consider this to the be API equivalent of the 'cluster show' command in the ONTAP CLI.