You can define your own RESTful end points, as an HTTP Request:
And then use it like this (copy the contents of the red box, above, to the URL):
Your handler will have access to the request object, as in this example:
Please note that this is a raw request object (more specifically an instance of HttpServletRequest), which is different than the request objects you get in other contexts (rules, events, etc...). This is because, when writing a handler, you are completely taking control -- Espresso will therefore not create a standard request object.