Welcome to the SmartThings Community, @Alexandre_Fraser!
The steps in the repo you shared belong to the Legacy platform (please, check this announcement).
The link @orangebucket shared belongs to the SmartThings API which you can use to send commands to your devices installed on ST.
To send commands (and make other requests), you need to create a Personal Access Token.
For example, this request is used to send a command to the colorControl capability of a device:
You would need to configure the PAT in the authorization tab as shown below:
How are you pinging this device? I mean, is it a program you developed separately?