APIC can be fully driven by its CLI and Rest Interface To create an subsription you need a payload like

{
  "product_url": "https://<manager url>/api/catalogs/<org>/<catalog>/products/<product id>",
  "plan": "default"
}

The product ID can be retrieved by listing the products

Then after logging in with the CLI use the following command to create the application.

apic-slim subscriptions:create -a <application>  -c <catalog> -o <org> -s <manager url> --consumer-org <consumer org> <path to the payload file>