mbt tool basically sends HCI command to the device and waits for an HCI Command Complete event from the device. You can use it to test the Bluetooth radio and RF performance.
Please follow the instructions given in the below user guide. (Check "UART Boot-Up" section in page number: 11). Those instructions will enable the device to accept HCI commands or download firmware through the UART interface. Please try it.
Some of the useful links are given below. Please have a look.