Hi Prachi, I hope you're doing well!
The IOT Toolbox Mobile Application is looking for a specific UUID to connect to the device via Bluetooth. The example has to use this UUID so it doesn’t get filtered out from the IOT Toolbox Mobile Application Device list, and this UUID is the one used by the hybrid BLE-Thread Wireless UART for the KW41Z.
This is not implemented in the Out-Of-Box example for the Rapid IOT prototyping kit and requires a custom implementation.
Please let me know if you need any more information.
Best regards,
Sebastian