Tokens and policy descriptors are used for dynamic on demand session management in a distributed and scalable architecture for on demand sessions and resource management. The architecture includes an on demand client, a purchase server, and a session manager. A purchase token is generated at the purchase server and assigned to the on demand client. The purchase token represents at least one requested asset. In response to an on demand session set-up request corresponding to the purchase token from the on demand client to the session manager, the purchase token is expanded to generate at least one dynamic policy management descriptor for the on demand session. This provides token-based purchase authorization and policy management for on demand services.