class BookRecommendationTools(Toolkit):
    """A toolkit for recommending books."""

    reading_level: Literal["beginner", "advanced"]

    @toolkit_tool() # not sure about this naming...
    def format_book(self, title: str, author: str) -> str:
        """Returns the title and author of a book nicely formatted.

        Reading level: {self.reading_level}
        """
        return f"{title} by {author}"

@openai_call(model="gpt-4o")
def recommend_book(genre: str, reading_level: Literal["beginner", "advanced"]):
    """Recommend a {genre} book."""
    toolkit = BookRecommendationTools(reading_level=reading_level)
    return {"tools": [toolkit.create_tools()]}