First problem:
the top right speech bubble icon re-appeared, the chat driven and chat enabled notebook options disappeared from the File menu

If I select "Install from URL" using the top-right dropdown menu then I get an error:

Do I need to reinstall the paclet?
Also, in your example does the line...
tool=LLMTool["cityPopulationFinder","city"->"City",#city["Population"]&]
...need to be set as initialization cell?
thanks!