Update prompts.yaml

prompts.yaml

@@ -9,6 +9,12 @@
   These print outputs will then appear in the 'Observation:' field, which will be available as input for the next step.
   In the end you have to return a final answer using the `final_answer` tool.
 
+  IMPORTANT TOOL USAGE RULES:
+  - For any web or internet search, you MUST use the tool `DuckDuckGoSearchTool`.
+  - Do NOT invent or call tools that are not explicitly provided.
+  - Do NOT use function names like `web_search`, `browser_search`, or similar.
+  - When you need information from the web, always call `DuckDuckGoSearchTool` with a search query string.
+
   Here are a few examples using notional tools:
   ---
   Task: "Generate an image of the oldest person in this document."