docs: update structured output how-to guide (#2773)

Fixes #2760

docs/docs/how-tos/react-agent-structured-output.ipynb

@@ -225,9 +225,19 @@
     "# Define the function that responds to the user\n",
     "def respond(state: AgentState):\n",
     "    # Construct the final answer from the arguments of the last tool call\n",
-    "    response = WeatherResponse(**state[\"messages\"][-1].tool_calls[0][\"args\"])\n",
+    "    weather_tool_call = state[\"messages\"][-1].tool_calls[0]\n",
+    "    response = WeatherResponse(**weather_tool_call[\"args\"])\n",
+    "    # Since we're using tool calling to return structured output,\n",
+    "    # we need to add  a tool message corresponding to the WeatherResponse tool call,\n",
+    "    # This is due to LLM providers' requirement that AI messages with tool calls\n",
+    "    # need to be followed by a tool message for each tool call\n",
+    "    tool_message = {\n",
+    "        \"type\": \"tool\",\n",
+    "        \"content\": \"Here is your structured response\",\n",
+    "        \"tool_call_id\": weather_tool_call[\"id\"],\n",
+    "    }\n",
     "    # We return the final answer\n",
-    "    return {\"final_response\": response}\n",
+    "    return {\"final_response\": response, \"messages\": [tool_message]}\n",
     "\n",
     "\n",
     "# Define the function that determines whether to continue or not\n",
@@ -466,7 +476,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.4"
+   "version": "3.12.3"
   }
  },
  "nbformat": 4,