Since bt-device --connect is the intended way to initiate a pairing operation, it needs to provide an optional --capability argument that the caller can use to specify the desired agent capability to use. For example:

• if the caller supplies DisplayYesNo, then the agent should not prompt the user for any input other than a yes/no confirmation
• if the caller supplies 'DisplayOnly', then the agent should not prompt the user for any input, only display things to them
• if the caller supplies 'KeyboardDisplay', then the agent should prompt the user for any needed kind of input (PIN, passkey, or yes/no confirmation) when the agent receives the appropriate callbacks from bluez