Version 2.4.0 added JSR-303 support for the models (#356).

For Request Parameters the following annotations could be supported as well:

• @SiZe
• @min
• @max
• @NotNull
  • @RequestParam: not necessary if using @RequestParam(required=true) / by default all request parameters are required
  • @ModelAttribute: necessary for parameters declared using a POJO/ @ModelAttribute

After Swagger-UI supports picking it up, it could be displayed/rendered in Swagger-UI as well:
swagger-api/swagger-ui#1936