https://phys.org/news/2018-06-google-prepping-duplex-bot-summer.html

For starters, Google says that the bot will identify itself as an automated assistant upfront and will disclose that it's recording calls. Human operators will be standing by as backup should a call go off the rails.

As for Duplex's tendency to use speech fillers like "ums" and "ahs," Google notes that this technique improved the assistant's ability to book appointments by interacting more naturally with humans on the other end of the line.