Identify the device
Document the model, identifier and installation context. Treat the device and its current site as separate records so it can move without losing history.
Describe the messages
For each message, record its fields, units and a typical payload. Include samples of reconnection and repeated events as well as a normal upload.
Connect events to operations
Ask the operator which events require a record, an alert or a human decision. Agree one end-to-end acceptance scenario before expanding the scope.