I'm just testing the REST Reports & Dashboards API using Workbench and I tried a quick test to download the results in a Formatted Excel format. I used the source code provided in the sample PDF (https://resources.docs.salesforce.com/sfdc/pdf/salesforce_analytics_rest_api.pdf)
Sample GET Request:
Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet; charset=UTF-8 Accept: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
UNSUPPORTED_MEDIA_TYPE errorCode: UNSUPPORTED_MEDIA_TYPE message: The Analytics API only supports JSON content type in both request and response bodies. Specify requests with content type as application/json.
I feel like this is a very basic rookie error I'm encountering - does anyone have some quick sample code they can share to show me the error of my ways. Thanks!