The Atlassian Jira Field Configuration Scheme API is a tool that allows users to define how and where custom fields appear in Jira issues. By using this API, administrators can create and configure field configuration schemes that determine which custom fields are available in different issue screens, such as create, edit, and view screens. This provides a flexible way to customize the fields that users see and interact with when working on Jira issues, allowing for better organization and visibility of important information. Additionally, the API enables administrators to easily manage field configurations across multiple projects and issue types, streamlining the process of setting up and maintaining custom fields in Jira.