[localhost:9999 /] /profile=default/subsystem=datasources/data-source="custom-datasource-name":add
{
    "outcome" => "failed",
    "result" => {"server-groups" => {"main-server-group" => {
        "server-one" => {
            "host" => "local",
            "response" => {
                "outcome" => "failed",
                "failure-description" => "Failed to create DataSource instance for [{
    \"operation\" => \"add\",
    \"address\" => [
        (\"subsystem\" => \"datasources\"),
        (\"data-source\" => \"custom-datasource-name\")
    ]
[...]

And then a subsequent read operation blows up:

 {
     "operation" : "read-children-resources",
     "address" : [
         {
             "PROPERTY_VALUE" : {
                 "profile" : "default"
             }
         },
         {
             "PROPERTY_VALUE" : {
                 "subsystem" : "datasources"
             }
        }
   ],
 "child-type" : "data-source"
}


[Host Controller] 10:18:06,349 ERROR [org.jboss.as.controller] (pool-2-thread-21) operation ("read-children-resources") failed - address: ([
[Host Controller]     ("profile" => "default"),
[Host Controller]     ("subsystem" => "datasources")
[Host Controller] ]): java.lang.IllegalArgumentException
[Host Controller] at org.jboss.dmr.ModelValue.getKeys(ModelValue.java:124)
[Host Controller] at org.jboss.dmr.ModelNode.keys(ModelNode.java:1085)
[Host Controller] at org.jboss.as.controller.operations.global.GlobalOperationHandlers$ReadResourceHandler.readModel(GlobalOperationHandlers.java:128)