Kinda tempted to say 424 or 402 and you should always consider 418. Actually 418 might be appropriate as the service was clearly not built to solve the problem

Kinda tempted to say 424 or 402 and you should always consider 418. Actually 418 might be appropriate as the service was clearly not built to solve the problem as it exists today. "The HTTP 418 I'm a teapot client error response code indicates that the server refuses to brew coffee because it is, permanently, a teapot."