1. One or more computer storage media having stored thereon multiple instructions that, when executed by one or more processors, cause the one or more processors to: receive, as one or more parameters of an application programming interface method invoked by a client application, information describing a type registration regarding which an action is being requested by the client application; determine, based on the one or more parameters, one of multiple type extensions to which the action being requested corresponds; and send at least part of the information describing the type registration to the one of the multiple type extensions for the one of the multiple type extensions to perform the action being requested.