1. A computing system, comprising: a processor; and a memory including instructions that upon execution by the processor cause the computing system to: receive an indication of a request from a program executing on a client device of a consumer, the request being to invoke an indicated invocable service from a service provider on behalf of the consumer, wherein the indicated invocable service is provided by the service provider from one or more computer systems remote from the client device; determine whether to authorize access of the consumer to the indicated invocable service based on an associated usage model for the indicated invocable service, the associated usage model including a use price for the invocable service or a use condition to control use of the invocable service, the determining being based, if the use price is included in the usage model, at least in part on whether payment is available for the use price, and the determining being based, if the use condition is included in the usage model, at least in part on whether the use condition is satisfied for the access; and if it is determined to authorize the access in accordance with the associated usage model, initiate invocation of the invocable service from the service provider on behalf of the consumer by performing one or more interactions with the one or more computer system, and otherwise not initiate the invocation.