Claude writes

Select a rough draft or your notes in any app and press ⌘⇧C. Claude writes it out in a tone that fits the place, in the same language: Enter puts it in place of the selection, ⌘⇧C again writes another version, Esc cancels. With nothing selected, it asks what to write. In a Claude Code session it writes your prompt; in a terminal (turn it on in its settings) it writes the command, with a warning if it deletes, overwrites or needs root, and runs it only on Enter.

It needs a Claude Pro or Max plan. Launcher › Settings › Claude writes sets the model and instructions of your own. What it sends is under Good to know.