The Guest Programming API The VMware Guest API provides functions that you can use in a program that runs in the guest operating system environment on a VMware ESXi host. Overview of the vSphere Guest APIThe vSphere Guest API provides functions that management agents and other software can use to collect data about the state and performance of a VMware virtual machine. The Guest API provides fast access to resource management information, without the need for authentication.How to Use the vSphere Guest APIThe vSphere Guest API defines functions and data types that you use to extract virtual machine data. This section covers the following topics: