Systems and methods are provided that use a trained process to reply to a request comprising query data defining a query and context data defining contextual factors for the query from a device. The query is answered by one or more selected APIs of a plurality of APIs that invoke respective services to prepare a response. The trained process determines an execution plan responsive to the query data and the context data and is configured using training to define execution plans comprising selected APIs where a particular API is selected for the plan if it answers at least a portion of the query and the selected APIs together prepare the response optimized for the device according to the context data. The plan is provided to an execution component to execute the plan using the selected APIs and send the response to the requesting device.