Fix AI agent tool-calling bug in RAG chatbot (Python + LangChain)

We need a developer to diagnose and fix a tool-calling issue in a RAG chatbot built with Python and LangChain. The current setup correctly calls the right tool but fails to pass the correct parameters, resulting in incorrect responses. You will review the existing code, identify the root cause, implement the fix, and verify that the chatbot now returns accurate results. This is a small, focused task for someone who can quickly troubleshoot and improve the tool-calling logic.