Posting json array with strings to Asp.Net MVC action controller is always null

I cannot get Asp.Net MVC to bind a list of strings sent as an json object unless I wrap them in a class. I have a hard time believing that it is a must to wrap the list like that. Been looking at various examples and what not for a few hours, but cannot get any other solution to work. What am I missing? Working and non-working code below.

$.ajax({
        type: "POST",
        traditional: true,
        url: "keyapi/activate.json",
        data: JSON.stringify({ "keys": [ "1", "2" ] }),
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            alert(data);
    }
});

When using an action controller such as the one below "keys" will be null.

[HttpPost]
public Response<List<string>> ActivateKeys(List<string> keys)
{
    return KeyService.ActivateKeys(test.Keys);
}

If I add a class to wrap the list it works. Am I forced to do so, or am I missing something here? The code below works, using the same jquery post code.

[HttpPost]
public Response<List<string>> ActivateKeys(Test test)
{
    return KeyService.ActivateKeys(test.Keys);
}
public class Test
{
    List<string> Keys { get; set; }
}