syncthing-rest-api(7) on Linux
The text 9f2f44036f50, as Debian 10 (Buster) shipped it.
REST API Syncthing exposes a REST interface over HTTP on the GUI port. This is used by the GUI (from Javascript) and can be used by other processes wishing to control Syncthing. In most cases both the input and output data is in JSON format. The interface is subject to change.