“ ta gnikooL .noitcirtser detnemucodnu na tsael ta ro ,gub a siht gnillac sa raf sa og neve dluow Ihttps://developers.google.com/workspace/add-ons/concepts/widgets#text_formatting indicates that "hyperlinks" are supported, but it doesn't indicate that, for example, <a href='tel:123456789'> doesn't work. ”