Integrating Single Sign-On (SSO) into a custom-built authentication system is a challenging task due to the complexity of protocols like SAML, OIDC, and OAuth, and the need to manage the entire SSO lifecycle, including metadata handling, domain routing, and integrating with Identity Providers (IdPs) like Microsoft Entra ID. These tasks become cumbersome as enterprise customers demand secure integration and full administrative control over authentication and access policies. Descope offers a solution by providing an out-of-the-box platform to extend existing authentication systems with enterprise-ready SSO support. This allows companies to maintain their existing login systems while leveraging Descope to handle the complex aspects of SSO, such as protocol intricacies and tenant routing. By using Descope, businesses can provide seamless login experiences, meet enterprise security expectations, and reduce the operational burden of maintaining custom integrations.