Custom metadata allows WorkOS to store custom string values on users and organizations, enabling applications to access context directly from authentication responses without disruption. JWT templates provide flexibility in customizing session JSON web tokens with metadata and claims, allowing developers to balance snappy retrieval of data with network round trips. External IDs simplify migrations by providing a unique identifier for users and organizations that can be used across existing authentication systems. These capabilities work together to deliver essential metadata directly from WorkOS, enhancing the overall developer experience.