Fix test instructions

tests/test_agency.py

@@ -489,7 +489,7 @@ def test_10_concurrent_API_calls(self):
         with open("./data/schemas/get-headers-params.json", "r") as f:
             tools = ToolFactory.from_openapi_schema(f.read(), {})
 
-        ceo = Agent(name="CEO", tools=tools, instructions="You are an agent that tests concurrent API calls.")
+        ceo = Agent(name="CEO", tools=tools, instructions="You are an agent that tests concurrent API calls. You must say 'success' if the output contains headers, and 'error' if it does not and **nothing else**.")
 
         agency = Agency([ceo], temperature=0)