Use customtool's get_tool_definition to remove duplication (#584)

# What does this PR do?

Current examples would cause a lot of unnecessary painful duplication
when a bunch of custom tools are expected while dealing with a real use
case.

Also added pip install -U httpx==0.27.2 to avoid a [httpx proxies
error](https://github.com/meta-llama/llama-stack-apps/issues/131) when
running in an env with 0.28 or higher of httpx installed by default.






In short, provide a summary of what this PR does and why. Usually, the
relevant context should be present in a linked issue.

- [ ] Addresses issue (#issue)


## Test Plan

Please describe:
 - tests you ran to verify your changes with result summaries.
 - provide instructions so it can be reproduced.


## Sources

Please link relevant resources if necessary.


## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Ran pre-commit to handle lint / formatting issues.
- [ ] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.

docs/zero_to_hero_guide/04_Tool_Calling101.ipynb

@@ -286,6 +286,9 @@
     "    input_shields = [] if disable_safety else [\"llama_guard\"]\n",
     "    output_shields = [] if disable_safety else [\"llama_guard\"]\n",
     "\n",
+    "    # Initialize custom tool (ensure `WebSearchTool` is defined earlier in the notebook)\n",
+    "    webSearchTool = WebSearchTool(api_key=BRAVE_SEARCH_API_KEY)\n",
+    "    \n",
     "    # Define the agent configuration, including the model and tool setup\n",
     "    agent_config = AgentConfig(\n",
     "        model=MODEL_NAME,\n",
@@ -296,18 +299,7 @@
     "            \"top_p\": 0.9,\n",
     "        },\n",
     "        tools=[\n",
-    "            {\n",
-    "                \"function_name\": \"web_search\",  # Name of the tool being integrated\n",
-    "                \"description\": \"Search the web for a given query\",\n",
-    "                \"parameters\": {\n",
-    "                    \"query\": {\n",
-    "                        \"param_type\": \"str\",\n",
-    "                        \"description\": \"The query to search for\",\n",
-    "                        \"required\": True,\n",
-    "                    }\n",
-    "                },\n",
-    "                \"type\": \"function_call\",\n",
-    "            },\n",
+    "            webSearchTool.get_tool_definition()\n",
     "        ],\n",
     "        tool_choice=\"auto\",\n",
     "        tool_prompt_format=\"python_list\",\n",
@@ -316,11 +308,8 @@
     "        enable_session_persistence=False,\n",
     "    )\n",
     "\n",
-    "    # Initialize custom tools (ensure `WebSearchTool` is defined earlier in the notebook)\n",
-    "    custom_tools = [WebSearchTool(api_key=BRAVE_SEARCH_API_KEY)]\n",
-    "\n",
     "    # Create an agent instance with the client and configuration\n",
-    "    agent = Agent(client, agent_config, custom_tools)\n",
+    "    agent = Agent(client, agent_config, [webSearchTool])\n",
     "\n",
     "    # Create a session for interaction and print the session ID\n",
     "    session_id = agent.create_session(\"test-session\")\n",

docs/zero_to_hero_guide/Tool_Calling101_Using_Together's_Llama_Stack_Server.ipynb

@@ -71,7 +71,8 @@
     }
    ],
    "source": [
-    "!pip install llama-stack-client==0.0.50"
+    "!pip install llama-stack-client==0.0.50\n",
+    "!pip install -U httpx==0.27.2 # https://github.com/meta-llama/llama-stack-apps/issues/131"
    ]
   },
   {
@@ -355,6 +356,9 @@
     "async def create_weather_agent(client: LlamaStackClient) -> Agent:\n",
     "    \"\"\"Create an agent with weather tool capability.\"\"\"\n",
     "\n",
+    "    # Create the agent with the tool\n",
+    "    weather_tool = WeatherTool()\n",
+    "    \n",
     "    agent_config = AgentConfig(\n",
     "        model=LLAMA31_8B_INSTRUCT,\n",
     "        #model=model_name,\n",
@@ -369,23 +373,7 @@
     "            \"top_p\": 0.9,\n",
     "        },\n",
     "        tools=[\n",
-    "            {\n",
-    "                \"function_name\": \"get_weather\",\n",
-    "                \"description\": \"Get weather information for a location\",\n",
-    "                \"parameters\": {\n",
-    "                    \"location\": {\n",
-    "                        \"param_type\": \"str\",\n",
-    "                        \"description\": \"City or location name\",\n",
-    "                        \"required\": True,\n",
-    "                    },\n",
-    "                    \"date\": {\n",
-    "                        \"param_type\": \"str\",\n",
-    "                        \"description\": \"Optional date (YYYY-MM-DD)\",\n",
-    "                        \"required\": False,\n",
-    "                    },\n",
-    "                },\n",
-    "                \"type\": \"function_call\",\n",
-    "            }\n",
+    "            weather_tool.get_tool_definition()\n",
     "        ],\n",
     "        tool_choice=\"auto\",\n",
     "        tool_prompt_format=\"json\",\n",
@@ -394,8 +382,6 @@
     "        enable_session_persistence=True\n",
     "    )\n",
     "\n",
-    "    # Create the agent with the tool\n",
-    "    weather_tool = WeatherTool()\n",
     "    agent = Agent(\n",
     "        client=client,\n",
     "        agent_config=agent_config,\n",
@@ -470,5 +456,5 @@
   }
  },
  "nbformat": 4,
- "nbformat_minor": 0
+ "nbformat_minor": 4
 }