How to use the Custom Web Search tool

[jqsl2012]

Question

I don't want to use the built-in WebSearchTool, I want to use a custom search tool.

After the program is run, it does output [debug] web_search_tool input query=xxx, but it also reports an error: agents.exceptions.MaxTurnsExceeded: Max turns (1) exceeded. How should I write my custom search function correctly?

@function_tool
def web_search_tool(query: str):
    print(f"[debug] web_search_tool input query={query}")
    return f"Search {query} result."


search_agent = Agent(
    name="Search agent",
    instructions=INSTRUCTIONS,
    tools=[web_search_tool],
    model_settings=ModelSettings(tool_choice="required"),
)

async def _search(self, item: WebSearchItem) -> str | None:
        input = f"Search term: {item.query}\nReason for searching: {item.reason}"
        try:
            result = await Runner.run(
                search_agent,
                input,
                max_turns=1
            )
            return str(result.final_output)
        except Exception:
            logger.exception("_search ex=")
            return None

[rm-openai]

You'll need max turns>1.

1. Turn 1: agent calls the web search tool. Tool runs, and tool result is appended to the history
2. Turn 2: agent receives the web search result and processes it. (Though in this case with tool_choice required, it will try to use the tool again)

[jqsl2012]

@rm-openai Thank you, I changed max_turns to 3 and the program works normally.

In addition, I also found that when adding model_settings=ModelSettings(tool_choice="required") to Agent, MaxTurnsExceeded will still appear when max_turns=3. However, max_turns=3 remains unchanged, and the program works normally when model_settings=ModelSettings(tool_choice="required") is commented out. I don't know why this happens at the moment.

[jaijuneja]

As a few folks have mentioned, setting tool_choice="required" seems to force the agent to use the web_search_tool at every iteration rather than processing the result. Best bet is to remove that setting and instead give a clear instruction to the agent to only run the web_search_tool once, which I've found to work reliably.

[rm-openai]

Yes, tool_choice=required can be a footgun. #203 helps with this.