I am trying to use the If-Modified-Since header with SObject Describe https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/describe_global_with_ifmodified_header.htm
I want to know if the contact object's metadata has been modified since the specified date. I am using the Workbench REST Explorer.
My Request Header is
Content-Type: application/json; charset=UTF-8
If-Modified-Since: Sat, 29 Jul 2017 00:00:00 GMT
and endpoint is
I have not made any changes to contact metadata but it is still returning metadata for contact instead of HTTP/1.1 304 Not Modified status code.