The present invention extends to using Simple Object Access Protocol (“SOAP”) to exchange typed objects, such as, for example, parameters for invoking methods. A computer system accesses typed object parameters corresponding to a typed object. The typed object is annotated with one or more message contract attributes of a message contract model defining a mapping between typed object parameters and corresponding SOAP elements. The computer system utilizes the message contract attributes to map the typed object parameters into a SOAP element and inserts the SOAP element into a SOAP envelope. A receiving computer system accessing the SOAP element and utilizes the message contract attributes to map the SOAP element back into the typed object parameters.