Netapp Storage automation using vra/vro

To creating a volume on oncommand unified manager(OCUM) and configured to it as datastore to esxi host. The step of automation needs from virtual realization automation(vRA) catalog. The catalog item should be like select the cluster and in that select aggregates and check the aggregate space available or not and assigning the volume. For that task alreaday 60% automated task completed. If any one knows about that i will explain that 60% part and remaining show it you what needs to be done. The 60% part is already integrated with oncommand unified manager (OCUM) and wfa . The wfa rest is created in vro. From vra catalog item select the cluster and assigning it to a esxi host but they wants like not selecting the cluster they want in that cluster select the aggregate (check space is available or not). The work is need from wfa side.