Matt Robb wanted to sell his computer keyboard. So he made a listing on Facebook Marketplace — and, as an experiment late last month, he put Meta's new artificial intelligence agent Muse in the driver's seat. “I kind of went into it like a guinea pig,” said Robb, a Toronto-based content creator who regularly reviews consumer tech. He had seen Muse's plush toy-looking avatar pop up on Instagram and decided to see if the AI agent could spare him some online bargaining. Muse got to work. a...