Your are definitely heading in the right direction but you might have the conversation a little backwards. After your device sends out a device announce packet (ZDO cluster 0x0013), it then needs to listen for packets from the SmartThings hub. When the hub receives your device announce packet it will send you a Report Active End Points request (ZDO cluster 0x0005). You need to respond to that packet with an Active End Point Response packet (ZDO cluster 0x8005). Here is another excerpt from my Nuts&Volts article mentioned above that details the conversation between a ZigBee device and the hub.
