Method to_function_tool

src/agents/mcp/util.py:504–573

Convert an MCP tool to an Agents SDK function tool. The ``agent`` parameter is optional for backward compatibility with older call sites that used ``MCPUtil.to_function_tool(tool, server, strict)``. When omitted, this helper preserves the historical behavior for static

(
        cls,
        tool: MCPTool,
        server: MCPServer,
        convert_schemas_to_strict: bool,
        agent: AgentBase | None = None,
        failure_error_function: ToolErrorFunction | None = default_tool_error_function,
        tool_name_override: str | None = None,
    )

    @classmethod
    def to_function_tool(
        cls,
        tool: MCPTool,
        server: MCPServer,
        convert_schemas_to_strict: bool,
        agent: AgentBase | None = None,
        failure_error_function: ToolErrorFunction | None = default_tool_error_function,
        tool_name_override: str | None = None,
    ) -> FunctionTool:
        """Convert an MCP tool to an Agents SDK function tool.

        The ``agent`` parameter is optional for backward compatibility with older
        call sites that used ``MCPUtil.to_function_tool(tool, server, strict)``.
        When omitted, this helper preserves the historical behavior for static
        policies. If the server uses a callable approval policy, approvals default
        to required to avoid bypassing dynamic checks.
        """
        tool_public_name = tool_name_override or tool.name
        static_meta = cls._extract_static_meta(tool)
        invoke_func_impl = functools.partial(
            cls.invoke_mcp_tool,
            server,
            tool,
            tool_display_name=tool_public_name,
            meta=static_meta,
        )
        effective_failure_error_function = server._get_failure_error_function(
            failure_error_function
        )
        schema, is_strict = copy.deepcopy(tool.inputSchema), False

        # MCP spec doesn't require the inputSchema to have `properties`, but OpenAI spec does.
        if "properties" not in schema:
            schema["properties"] = {}

        if convert_schemas_to_strict:
            # ``ensure_strict_json_schema`` mutates the schema in place and may raise
            # partway through, leaving strict-mode artifacts (e.g. ``required`` or
            # ``additionalProperties: false``) on a schema we still serve as
            # non-strict. Convert a separate copy so the non-strict fallback keeps
            # the original schema intact.
            try:
                schema = ensure_strict_json_schema(copy.deepcopy(schema))
                is_strict = True
            except Exception as e:
                logger.info(f"Error converting MCP schema to strict mode: {e}")

        needs_approval: (
            bool | Callable[[RunContextWrapper[Any], dict[str, Any], str], Awaitable[bool]]
        ) = server._get_needs_approval_for_tool(tool, agent)

        function_tool = _build_wrapped_function_tool(
            name=tool_public_name,
            description=resolve_mcp_tool_description_for_model(tool),
            params_json_schema=schema,
            invoke_tool_impl=invoke_func_impl,
            on_handled_error=_build_handled_function_tool_error_handler(
                span_message="Error running tool (non-fatal)",