What does rpc.pingomatic.com respond with to valid pings?

I keep getting an http 200 response code but no actual response when pinging pingomatic via the API.

Is this normal? Is my script working?

I am confused because weblogs.com shoots back a friendly “thanks for the ping!” bit of XML after a successful ping.

I can’t seem to find any documentation on pingomatic API anywhere.

Matt Mullenwegg writes that he created one, but there are no links on this page: https://blog.pingomatic.com/2006/01/16/internal-api-complete/

I suppose it would make sense however as simple visiting https://rpc.pingomatic.com in your browser shows an ugly error, where https://rpc.weblogs.com/RPC2 shows pretty and perfect xml syntax as a response.