List of API callbacks Defines a single callback in the API. The name attribute defines the callback name and the group attribute is used to group similar calls in the generated documentation. Description of the callback. Defines the callback output. The argument type defaults to xsd:string if not specified. The argument name defaults to [type]Value where [type] is the argType value with the namespace designator removed. Description of the output argument. Defines a callback input argument. The argument type defaults to xsd:string if not specified. The argument name defaults to [type]Value where [type] is the argType value with the namespace designator removed. Description of the input argument. Specifies the API version at which this API call was modified. The modificationType attribute indicates the type of change. Valid changes types nclude: new -- implying an API call added in the specified version of the API, invalid -- implying that the specified call has been invalidated as of the specified version of the API, and modified -- implying that the API call functionality has been chagned as of the specified version of the API.