Hypothes.is is an online annotation tool https://hypothes.is/ AGU has implemented Hypothes.is in GEMS to allow a richer review process. It allows for inline comments and organizes these by reviewers, editors, and authors, and importance. Authors can respond inline to review comments. We will encourage reviewers to use this tool for their review, although it is entirely optional. As an editor, you can also place all your comments in an annotated manuscript, including your summary. If you do this, simply write “see annotated manuscript.” Reviewers and editors will remain anonymous in the annotation list (identified as “reviewer 1” etc.)
Further instructions are here.