Before using the API you should know that the BASIC tier has certain coverage restrictions in-place (PRO plan or higher removes these restrictions completely).
BASIC/FREE tier restrictions:
For an in-depth documentation visit https://highlightly.net/documentation/rugby/.
There you will find supported query parameters and routes with live examples.
Note: If you wish to use other Highlight APIs as well it might be better to switch to Sport Highlight API where all sports are available. Check https://highlightly.net/ for more information.