There are two slightly different versions (itch.io version and Arcana version) of each of the following generators: Perilous Shores, MFCG, NG, Procgen Mansion, VG, 1PDG. For example, for MFCG the web address of its itch.io version is https://watabou.itch.io/medieval-fantasy-city-generator and the web address of its Arcana version is https://watabou.github.io/city-generator/. Only the Arcana versions of the generators can access the address bar of your browser and pull parameters from there. You can't parameterize the itch.io version of a generator via a url, because on itch.io applications are run isolated (in an iframe).
Here is the same city with and without a castle (note the castle parameter in the urls):