nova/doc/api_samples/os-volumes/v2.85/attach-volume-to-server-resp.json

{
    "volumeAttachment": {
        "delete_on_termination": true,
        "device": "/dev/sdb",
        "id": "a07f71dc-8151-4e7d-a0cc-cd24a3f11113",
        "serverId": "09b3b9d1-b8c5-48e1-841d-62c3ef967a88",
        "tag": "foo",
        "volumeId": "a07f71dc-8151-4e7d-a0cc-cd24a3f11113"
    }
}