Controlling runtime access to application program interfaces

The present invention extends to methods, systems, and computer program products for controlling runtime access to application programming interfaces Embodiments of the invention allow library developers to more precisely and easily control which of their libraries' APIs can be called dynamically. Thus, their servicing and versioning burden can be more appropriately controlled. Further, application developers can control which such APIs to further exclude from dynamic calling scenarios, to minimize the runtime support overhead (e.g., preventing generation of metadata).