I have used the additional options via during data-type configuration.

[DotNetDataSource(Title="Example Property", Description="example description")]
  public string ExampleProperty { get; set; }

I notice that in the flickr extension you set

[DotNetDataSource(Title = "Flickr API Key", Description = "(required)")]
        public string ApiKey { get; set; }

With the description as "required" suggesting that we can't force the parameter to mandatory.

I've tried decorating parameters with [Required] also doesn't force mandatory

Perhaps there isn't a mechanism for making datatype params mandatory???

Am I missing a trick?

I did see the [ValidationProperty("isValid")] decorator mentioned for classes, but that's not quite what is required, and unsure if this would work in this instance?