The purpose of these Guardrails is to promote consistency and provide guidance around the use of Application Programming Interfaces (APIs) across ESDC, and to enable exchange and integration of data between systems, agencies, businesses and citizens. • Why API First? – APIs are an efficient and secure way to share data and expose functionality between government's digital services. "API First" is a design principle which stipulates that an API is the first interface for a given application; it is the first artefact to be developed over the data layer, and it is self described. • What's in the API Guardrails? – the ESDC API Guidelines provide design and best practices for building interfaces between systems or exposing data for secondary use. Other topics include security, metadata, versioning and management. The guidelines have been developed by ESDC using internal references and a thorough review of several public and private sector leaders. • When to use the API Guardrails? – most real time data integration requirements are best satisfied through APIs. In general, data sharing and integration also encourage the use of APIs to promote platform independence and loosely coupled service design.