It seems a little odd/inconsistent that for `with(n).arguments`, `with` is it's own method with `arguments` being chained on it afterwords..but here, `with` is just the first word of the full method name.  We could do

``` ruby
respond_to(:message).with(:x, :y).keyword_arguments
```

...I'm not sure that reads well, though.  Honestly, I'm not sure which way I prefer.  Just bringing it up for discussion.