I just worked it out from this post http://groups.google.com/group/google-web-toolkit/browse_thread/thread/947e7ba3e6c6686a:
@Prefix("!search") public static class Tokenizer implements PlaceTokenizer<SearchPlace> { } produces /wf.html#!search: -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.