What tools do you recomend for BLE debugging?

On Android, nRF Connect is a very useful and powerful generic BLE tool that lets you observe adverts, connect to devices and exchange data with a GATT server. 

For iOS, BLExplr provide similar functionality to MCP but is not free. It is also possible to use Wireshark in conjunction with a BL600/620 dev board or BL620-US running special sniffer firmware to provide over the air (OTA) sniffing functionality. Please contact support  for more information on setting up a BLE sniffer.