Conditional tool calls

Run the first two cells to install the libraries and re-define the tools

• Re-bind the LLM with the tools to make it tool-aware.
• Create nodes for the LLM and tools called "llm" and "tools", respectively
• Add the edges to enable conditional tool use: add standard edges connecting the LLM to START and END, and create a conditional edge to route to "tools" if the tool_condition function is met, and END if not.