A template is a container under which every Query Parameter is created.
Every Rebrandly workspaces comes with a build-in template. You can fetch a workspace's template calling the following endpoint:

GET /templates

Example of a valid request

$ curl 'https://templating.rebrandly.com/v1/url/querystring/templates' \
-X GET \
-H 'apikey: YOUR_API_KEY' \
-H 'workspace: YOUR_WORKSPACE_ID' \
-H 'Content-Type: application/json'

A 200 response for this request is

        "id": "<TEMPLATE_ID>",
        "name": "Main Template",
        "createdAt": "2022-11-17T15:25:18Z"

You can assume there's always 1 template in the returned array so you can get response[0].id as the template ID to build every other endpoint's path.

Now that you have a template ID, you can start operating on your query parameters.