fix: prompting and answers

agent.py

@@ -184,7 +184,10 @@ def build_graph(provider: str = "openai"):
     # Node
     def assistant(state: MessagesState):
         """Assistant node"""
-        return {"messages": [llm_with_tools.invoke(state["messages"])]}
+        # Prepend the system prompt
+        messages = [sys_msg] + state["messages"]
+        result = llm_with_tools.invoke(messages)
+        return {"messages": [result]}
     
     def retriever(state: MessagesState):
         """Retriever node"""