Taste Profile Update Request invalid JSON

Hello!

I just have a quick question on updating profiles. I've been getting back an invalid json error ("Invalid item block in the input: data is not properly json-encoded") when hitting the following URL:

...v4/catalog/update?api_key=&data_type=json&format=json&id=

and the following JSON:

[{"item":{"item_id":"royks","artist_name":"Royksopp"}},{"item":{"item_id":"inter","artist_name":"Interpol"}}]

I tried the following CURL command to try and isolate the problem from my javascript call:

curl -X POST "http://developer.echonest.com/api/v4/catalog/update" -F "api_key=" -F "data_type=json" -F "format=json" -F "id=" -F "data=@jsonSample.json" {"response": {"status": {"version": "4.2", "code": 5, "message": "id - Invalid parameter: id must be an Echo Nest id or foreign id"}}}

I've run my JSON through JSLint, so not sure what I'm missing.

Thanks!!