validated_params block create an endpoint specific requirement. By validating the params it creates a validated_params content too, so you don't have to parse content with hand afterhand.
When you need use custom parser, such as JSON, you can use that too, there is two one requirement to do so:
- implement the .parse(unserialized_string) interface
- raise any kind of exception if the given string is malformed
you can access during the endpoint block the validated values under the validated_params method
Have fun! :)