Tags are key-value pairs associated with a resource, in our case an instance.
Tags can be queried by the instance itself in order to take these values into account for its configuration.
Tags can only be created once the instance is created. After your instance is created, go to the COMPUTE menu, choose the INSTANCES section, and click on your instance to display the instance details. In the instance tags area of the instance details page, you can add a key and its corresponding value.
Tags can be accessed directly from the instance. You will need to access the Exoscale API, querying the instance tags. See the API documentation.