To provide a client with access to an API available from a provider, a request is received from a marketplace to subscribe to the API, responsive to the client selecting the API from a catalog of the marketplace. A subscriber identifier, which is uniquely associated with the request by the client to subscribe to the selected API, is generated. An authorization record is created within a proxy; it indicates that a request by the client to invoke the API received by the proxy should be forwarded to the provider from which the API is available if the request to invoke the API includes the subscriber identifier. The generated subscriber identifier and an address of the proxy are provided to the marketplace. Thus, the client is configured to invoke the API by sending a request including the subscriber identifier to the address of the proxy.