nova/doc/api_samples/all_extensions/server-create-req.json

{
    "server" : {
        "name" : "new-server-test",
        "imageRef" : "70a599e0-31e7-49b7-b260-868f441e862b",
        "flavorRef" : "1",
        "metadata" : {
            "My Server Name" : "Apache1"
        }
    }
}