This documentation describes the available application programming interface (API) or REST webservice interface in vtiger CRM through examples. It is understood as a reference and learning document for programmers wanting to use the API. For the most part it is a set of code examples on each of the available functions and a gathering of information on this topic in various conversations collected in forums and mailing lists and our own experience in using it. It makes constant reference to the availale online documentation about the subject.