Is using hydra built package declaratively possible?

Hello folks,

I recently learned that you can install packages successfully built on hydra using the nix-env call revelead by the Summary > Build products > Help Action button.

Is it somehow possible to install that same closure declaratively as in

(import (builtins.fetchTarball "https://hydra.nixos.org/build/116518901/download/1/cachix") {})

How would I determine the corresponding url (i. e. smth like https://hydra.nixos.org/build/116518901/download/1/cachix see this comment) ?