Variable types

bool true/false value
int 32-bit integer
double decimal number
string UTF-8 string in JSON/XML or URL encoded string in URL query
date date formatted as "yyyy-MM-dd", e.g. "2012-01-05" for 5th January 2012
timestamp date and time formatted as "yyyy-MM-ddTHH:mm:ssZ" (ISO 8601)
color ARGB color, e.g. "#7FFFF500" for semi-transparent yellow
array array of int, string, object or other types
object custom type, additionally described in the documentation

Data formats

In general methods can handle user-preferred JSON (application/json) or XML (application/xml) while import/export methods support CSV, XLS, XML, ZIP formats.
Data format is defined in Accept header, e.g. request with Accept: application/json returns data formatted as JSON while Accept: application/xml returns XML data. Default content type is JSON in case Accpet header is missing.