Templates appear as one-tap chips above the message box. Use curly braces for blanks, e.g. SETSERVER,{ip},{port} — you'll be asked to fill each blank when you tap the chip.

These values come from the SMS Gateway for Android app on the gateway phone (Local Server mode). The IP and password are shown on the app's home screen.

Enter this computer's address as the phone sees it (same Wi-Fi network), then register the webhook so the phone pushes incoming SMS here.