# About the MetraTech APIs

A MetraTech Application Program Interface (API) is a set of routines, protocols, and tools that system integration developers use to provide customer solutions with the MetraTech platform.

The MetraTech APIs include:

- COM Objects - an instance of a COM class.

- Command Line Tools - utility programs executed from the DOS or Unix command line.

- Interfaces - code that is used by other MT components (such as COM objects, adapters, plug-ins) to standardize interactions with the Pipeline.

- Pipeline Stages - groups of plug-ins that perform specific functions (such as tax calculation or rounding). A pipeline is composed of one or more stages.

- Plug-ins - generic programs that process data for the Pipeline. One or more Plug-ins form a Stage.

- Service Definitions - XML configuration files that define the properties of a service.

In addition, MetraTech online Help also includes the following supporting information related to APIs:

- Enumerated Types - a user-defined type consisting of a set of named constants called enumerators.

- Error Codes - documentation of all error codes returned by MetraTech software and guidelines for handling errors.