Current pipe implementation does just support :

void read(Callback<List<T>> callback);

void readWithFilter(ReadFilter filter, Callback<List<T>> callback);

Is it planned to add a "read" by a given ID?
Something like this.

void readByID(Integer id, Callback<T> callback);

The idea is the following:

route().from("/cars/{id}").on(RequestMethod.GET).produces(CUSTOM_ALL_DETAILS).to(Cars.class).findById(param("id"));

route().from("/cars").on(RequestMethod.POST).produces(CUSTOM_MIN_DETAILS).to(Cars.class).getAll();

Having these routes, the"getAll" route returns only a minimum of details (model,...)
The "findByID" is returning all the details of the car including some related informations.

Returning full details for the getAll method would be overkill.