vCloud API - provides support for developers who are building interactive clients of VMware vCloud Director using a RESTful application development style.

VMware provides a comprehensive vCloud API Programming Guide. vCloud API clients and vCloud Director servers communicate over HTTP, exchanging representations of vCloud objects. These representations take the form of XML elements. You use HTTP GET requests to retrieve the current representation of an object, HTTP POST and PUT requests to create or modify an object, and HTTP DELETE requests to delete an object.
The guide is intended for software developers who are building VMware Ready Cloud Services, including interactive clients of VMware vCloud Director. The guide discusses Representational State Transfer (REST) and RESTful programming conventions, the Open Virtualization Format Specification, and VMware Virtual machine technology.

The vCloud API Programming Guide for vCloud Director 5.5 can be found here: http://pubs.vmware.com/vcd-55/topic/com.vmware.ICbase/PDF/vcd_55_api_guide.pdf