https://www.ietf.org/archive/id/draft-ietf-oauth-resource-metadata-13.html#section-5.1

The HTTP response code is 400 in the example in this section. However the error description is "No access token was provided in this request". According to the error codes section of RFC6750, if no access token is provided, the RS should not include an error code at all, and should respond with HTTP 401.

I recommend we update the example in the RS Metadata draft to be consistent with RFC6750, since RS Metadata refers to that draft for the error codes already:

The HTTP status code and error string in the example response above are defined by [RFC6750].