An API that you send comments and it tells you if it is spam or not (free for personal use and low traffic commercial sites IIRC). It is the spam-catching-backe

An API that you send comments and it tells you if it is spam or not (free for personal use and low traffic commercial sites IIRC). It is the spam-catching-backend for WordPress sites and many other forums -- like discourse, I think -- (so they have a really, really good idea of what spam looks like across billions of sites).