Catch and return tool validation errors to LLM

Wrap tool.ainvoke() in try/except to catch validation errors and send
them back to the LLM as error messages in ToolMessage. This allows the
LLM to see what went wrong and retry with correct arguments.

Author: abrookins

python-recipes/context-engineering/notebooks/section-3-memory/04_memory_tools.ipynb

@@ -275,13 +275,18 @@
         "        # Find and execute the tool\n",
         "        tool = next((t for t in memory_tools if t.name == tool_call['name']), None)\n",
         "        if tool:\n",
-        "            result = await tool.ainvoke(tool_call['args'])\n",
-        "            print(f\"   Result: {result}\")\n",
+        "            try:\n",
+        "                result = await tool.ainvoke(tool_call['args'])\n",
+        "                print(f\"   Result: {result}\")\n",
+        "                result_content = str(result)\n",
+        "            except Exception as e:\n",
+        "                print(f\"   Error: {e}\")\n",
+        "                result_content = f\"Error: {str(e)}\"\n",
         "            \n",
         "            # Add tool result to messages\n",
         "            messages.append(response)\n",
         "            messages.append(ToolMessage(\n",
-        "                content=str(result),\n",
+        "                content=result_content,\n",
         "                tool_call_id=tool_call['id']\n",
         "            ))\n",
         "    \n",
@@ -336,14 +341,19 @@
         "        # Find and execute the tool\n",
         "        tool = next((t for t in memory_tools if t.name == tool_call['name']), None)\n",
         "        if tool:\n",
-        "            result = await tool.ainvoke(tool_call['args'])\n",
-        "            print(f\"\\n   Retrieved memories:\")\n",
-        "            print(f\"   {result}\")\n",
+        "            try:\n",
+        "                result = await tool.ainvoke(tool_call['args'])\n",
+        "                print(f\"\\n   Retrieved memories:\")\n",
+        "                print(f\"   {result}\")\n",
+        "                result_content = str(result)\n",
+        "            except Exception as e:\n",
+        "                print(f\"\\n   Error: {e}\")\n",
+        "                result_content = f\"Error: {str(e)}\"\n",
         "            \n",
         "            # Add tool result to messages\n",
         "            messages.append(response)\n",
         "            messages.append(ToolMessage(\n",
-        "                content=str(result),\n",
+        "                content=result_content,\n",
         "                tool_call_id=tool_call['id']\n",
         "            ))\n",
         "    \n",