diff --git a/function_calls/llm.py b/function_calls/llm.py
index a364068..39356ec 100644
--- a/function_calls/llm.py
+++ b/function_calls/llm.py
@@ -74,12 +74,22 @@ class FunctionCallLLM:
         openai_functions = self._build_functions_for_openai(functions)
         messages: List[Dict[str, Any]] = []
 
-        system_prompt = (
+        custom_prompt = None
+        system_msg = getattr(chat_model, "system_content_msg", None)
+        if isinstance(system_msg, dict):
+            custom_prompt = system_msg.get("content")
+        elif isinstance(system_msg, str):
+            custom_prompt = system_msg
+        if custom_prompt:
+            messages.append({"role": "system", "content": custom_prompt})
+
+        tool_prompt = (
             "You are an assistant that can call tools. "
             "When you invoke a function, wait for the tool response before replying to the user. "
             "Only deliver a final answer once you have enough information."
         )
-        messages.append({"role": "system", "content": system_prompt})
+        messages.append({"role": "system", "content": tool_prompt})
+
         messages.append({"role": "user", "content": ctx.text})
 
         for round_index in range(self.max_function_rounds):