@silverwizard I'm looking at this as a web application returning a response code. HTTP is a protocol; some of the participants of that protocol will be extremely content aware, others less so. The very notion that holding coffee violates a teapot's nature is a philosophical conceit that would be odd for a low awareness system to express in the first place.
On the other hand, I suppose that attempting to french press in a teapot would be my idea of a 500-series teapot error.