An endpoint system provides a REST endpoint for an application. The endpoint system processes request messages based on message pair data for each message that includes an operation and parameter data. The parameter data includes parameter information for each parameter that identifies whether the value for the parameter is to be taken from the URI or payload of a request message. The endpoint system receives request messages that have a URI and payload. The URI includes an operation name. The endpoint system processes each request message in accordance with the message pair data for the operation specified in the request message. For each parameter of the message pair data, the endpoint system extracts the value for the parameter from either the URI or payload as specified by the parameter information for the parameter. The endpoint system then invokes the operation passing the one or more extracted values as actual parameters.