Atom Feeds /describe command is rerutning HTTP 401 unauthorized

Hi experts,

while trying to invoke Atom feeds describe path (e.g. hcmRestApi/atomservlet/employee/empupdate/describe) I'm getting HTTP 401 unauthorized

invoking /hcmRestApi/resources/11.13.18.05/workers/describe I'm able to fetch the rest API response decriptor as expected

Any idea on which could be the root cause for this? Permissions issue?

Thanks,

Massimiliano