The document discusses the System for Cross-domain Identity Management (SCIM) API. SCIM defines a schema and protocol for provisioning and managing user identity data across multiple applications and cloud services. It aims to standardize how user data is synchronized and provisioned between identity management systems and applications. The document outlines SCIM's features, provides examples of how it can be used, and discusses lessons learned from its design process, including the need for extensibility, versioning, error handling, and avoiding HTTP method overloading.