Add documentation for how to use tools and response_model together

[willbakst]

Description

We just released functionality for this in v1.14. Although you can infer the usage from type hints, it's better to be explicit. We should include documentation with examples demonstrating exactly how to use this feature.

[willbakst]

We should also make sure we cover a few other minor items such as common call params and clarifying the difference between custom clients and custom llm providers

[willbakst]

@Mizokuiam any idea on when you'll have the time to tackle this? Happy to assign the issue to you if you're available.

I think this documentation is important, so if you don't have the time just let us know :)