If you have a weather tool available it will be in a list of available tools, and the LLM may or may not ask to use it; it is not certain that it will, but if it is a 'reasoning' model it probably will.

You need to be careful creating a ton of tools and displaying a list of all of them to the model since it can overwhelm them and they can go down rabbit holes of using a bunch of tools to do things that aren't particularly helpful.

Hopefully you would have specific prompts and tools that handle certain types of tasks instead of winging it and hoping for the best.