Create an Asana task with External Data

I am having trouble creating an asana task with external data. I can create a task fine, but i can't figure out what the cocktail is to be able to use the "external" data that is mentioned in the documentation.

$.ajax({
   url : global.task.url,
   type: "post",
   data: {
    assignee: "my-email@hidden.com",
    name: "Test task",
    notes: "this is a note",
    projects: 123123123123,
    workspace: global.workspace,
    external: {
     "id": "test",
     "data": "12345099"
    }
   },
   beforeSend: function (xhr) {
    xhr.setRequestHeader("Authorization", "Bearer " + "MY-TOKEN");
   }
 })

the above code results in a 500 bad request.

I have also tried sending external stringified, which results in the error "No matching route for request".

The code above works perfectly if i remove the "external" from data.

i will be the first to say i do not typically call APIs so i feel like i must be doing something silly. any help appreciated!

UPDATE:

i was able to create a task by passing in external as:

'external.id' = "test",
'external.data' = "123123123"

however, i do not see the external data i generated, so there is still something going on.

UPDATE (2):

if i run the code below, i will get a 500 server error. if i comment out the "external" piece in the data, the tasks adds correctly.

$.ajax({
 url : "https://app.asana.com/api/1.0/tasks",
 contentType: "application/json",
 type: "post",
 beforeSend: function (xhr){
  xhr.setRequestHeader("Authorization", "Bearer " + settings.token);
 },
 data: JSON.stringify({
  data: {
   assignee: "my-email@hidden.com",
   name: "Test task",
   notes: "this is a note",
   projects: [5555555555555], //not the real one i am passing in
   external: {
    id: "testID",
    data: "some sweet data"
   },
   workspace: 555555555555 //not what i am really passing in
  }
 })
})

Could it be you already created a record with the id test? The IDs are unique - they have to be, or you couldn't use it for access. Try a random ID or something? You can always GET /tasks/external:test and see if there's a task there.