Hearing system, accessory device, agent and method for situated design of a hearing algorithm of a hearing device is disclosed, the method comprising initializing a model comprising a parameterized objective function; providing one or more operating parameters indicative of the hearing algorithm to the hearing device; obtaining operating data comprising corresponding input data and output data of the hearing device; obtaining evaluation data indicative of user evaluation of the output data; determining one or more updated operating parameters based on the model, the operating data and the evaluation data; and providing the updated operating parameters to the hearing device.