VMware provides several public API and Software Development Kits (SDK) products. You can use these products to interact with the following areas:
- host configuration, virtualization management and performance monitoring (vSphere Web Services API provides the basis for VMware management tools - available through the vSphere Web Services SDK). VMware provides language-specific SDKs (vSphere SDKs for Perl, .NET, or Java)
- server hardware health monitoring and storage management (CIM interface compatible with the CIM SMASH specification, storage management through CIM SMI-S and OEM/IHV packaged CIM implementations)
- extending the vSphere Client GUI (vSphere Client Plug-In API)
- access and manipulation of virtual storage - VMware Virtual Disk Development Kit (VDDK with library of C functions and example apps in C++)
- obtaining statistics from the guest operating system of a virtual machine (vSphere Guest SDK is a read-only programmatic interface for monitoring virtual machine statistics)
- scripting and automating common administrative tasks (CLIs that allow you to create scripts to automate common administrative tasks. The vSphere CLI is available for Linux and Microsoft Windows and provides a basic set of administrative commands. vSphere PowerCLI is available on Microsoft Windows and has over 200 commonly-used administrative commands.

Details Here: https://communities.vmware.com/community/vmtn/developer/