Implementing OAuth for secure, token-based authentication for external applications accessing the Metadata API Implementing OAuth for secure, token-based authentication is crucial when allowing external applications to access the Metadata API. This ensures that only authorized applications can access the API, enhancing security by providing controlled access based on authenticated tokens. Option A is incorrect because unrestricted access can lead to security vulnerabilities and performance issues. Option B is incorrect as real-time updates are more related to the functionality of the Metadata API rather than its configuration for external applications. Option D is incorrect because direct database access is not a standard or safe practice for external applications, especially in the context of API access.