kinetic_cafe_error provides an API-smart error base class and a DSL for defining errors. Under Rails, it also provides a controller concern (KineticCafe::ErrorHandler) that has a useful implementation of +rescue_from+ to handle KineticCafe::Error types. Exceptions in a hierarchy can be handled in a uniform manner, including getting an I18n translation message with parameters, standard status values, and meaningful JSON representations that can be used to establish a standard error representations across both clients and servers.