The HomeMatic CCU-Jack Special Agent add-on monitors HomeMatic CCU and RaspberryMatic systems through the CCU-Jack REST interface. It retrieves HomeMatic datapoints, service messages, device availability, battery states, and duty-cycle information and makes them available as Checkmk services. CCU-Jack is a REST- and MQTT-based interface for the CCU; the special agent uses its REST API specifically for Checkmk monitoring. No dedicated Checkmk agent needs to be installed on the CCU. In contrast, Tcl/ReGa-based agents query data through the CCU’s ReGaHSS/Tcl interface. In larger installations with many devices or datapoints, CCU-side return handling may reach size-related limits, potentially causing incomplete responses and missing values.