You receive a Web Services Error 612 on a REST API call
The 612 error code denotes that there was an invalid Content Type in the REST API call. If you see this error, add a content type header specifying JSON format to your request. For example, try using "content type: application/json".
Since this error is in the formatting of the REST API call that is being made to the Marketo instance, we recommend working with a developer to update the API call to resolve the error message. Here is a Link to StackOverflow that helps to discuss this kind of error message further: (http://stackoverflow.com/questions/28181325/why-invalid-content-type).
Who This Solution Applies To
Customers using REST API