Update prompts.yaml

prompts.yaml

@@ -299,6 +299,12 @@
     After writing the final step of the plan, write the '\n<end_plan>' tag and stop there.
 
     Now write your new plan below.
+
+final_answer: |-
+  You are about to finish. Compose the final user-facing response using only verified info.
+  Do NOT include Thought/Code/Observation.
+  Return it by calling the `final_answer` tool with one string argument.
+
 "managed_agent":
   "task": |-
     You're a helpful agent named '{{name}}'.