Outbound Calling - Wait for Answer

I’m using Asterisk to place outbound calls using Asterisk-Java, the AGI Script interface, swift for TTS, and using a Voip.ms SIP trunk. I’m using a STREAM FILE command to actually play the audio file generated by swift.

Everything is working but the TTS seems to start even before the user answers resulting in the user getting a partial message. Is there anyway to have the swift audio file played after the user has actually answered the phone instead?