Call https://demo.matomo.cloud/index.php?module=API&method=API.getMatomoVersion&token_auth=TOKEN_AUTH (yes, the authentication token is wrong, this is wanted)
If an error occurs, the HTTP response code should not be
4xx (in case of request error, in my case I am not authenticated so the HTTP error code should be
5xx (in case of server error or misconfiguration)
I am not authenticated, I receive an error message, but the HTTP response is
200: OK "everything seems good"
In case of error message (error result), never use HTTP
200, but at least HTTP
400 or HTTP
Just fyi this might affect various monitors and could break BC. So I'm putting this for now into Matomo 5 where we can consider doing this.