OAuth 2.1 serves as the foundation for the Model Context Protocol (MCP) by providing a robust framework for API authorization, yet the transition from traditional user interactions to agent-driven systems introduces unique challenges. While OAuth's classic roles—resource owner, client, resource server, and authorization server—remain, the MCP architecture requires a shift to multi-hop paths where authorization must travel through several intermediaries, raising concerns about sequence-level risks and credential leakage. To mitigate these risks, enterprises are advised to use Resource Indicators for token scoping, implement short-lived and server-specific tokens, and ensure rigorous credential management to prevent leakage into AI model contexts. Emerging patterns such as gateway-based authorization are being adopted to centralize policy enforcement and manage the complex interactions intrinsic to agent systems. As organizations deploy OAuth 2.1 for MCP, they must anticipate evolving security needs, including sequence-aware authorization, and adapt their architectures to accommodate these changes, leveraging existing infrastructure and best practices from OAuth's established ecosystem.