microsoft/autogen · error · ValueError

Unsupported server params type: {type(self._server_params)}

Error message

Unsupported server params type: {type(self._server_params)}

What it means

Error "Unsupported server params type: {type(self._server_params)}" thrown in microsoft/autogen.

Source

Thrown at python/packages/autogen-ext/src/autogen_ext/tools/mcp/_workbench.py:474

        else:
            error_message += f"{str(error)}\n"
        return error_message

    async def start(self) -> None:
        if self._actor:
            warnings.warn(
                "McpWorkbench is already started. No need to start again.",
                UserWarning,
                stacklevel=2,
            )
            return  # Already initialized, no need to start again

        if isinstance(self._server_params, (StdioServerParams, SseServerParams, StreamableHttpServerParams)):
            self._actor = McpSessionActor(self._server_params, host=self._host)
            await self._actor.initialize()
            self._actor_loop = asyncio.get_event_loop()
        else:
            raise ValueError(f"Unsupported server params type: {type(self._server_params)}")

    async def stop(self) -> None:
        if self._actor:
            # Close the actor
            await self._actor.close()
            self._actor = None
        else:
            raise RuntimeError("McpWorkbench is not started. Call start() first.")

    async def reset(self) -> None:
        pass

    async def save_state(self) -> Mapping[str, Any]:
        return McpWorkbenchState().model_dump()

    async def load_state(self, state: Mapping[str, Any]) -> None:
        pass

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Use stdio or SSE server params

Example fix

Pass StdioServerParams or SseServerParams

When it happens

Trigger: Thrown at python/packages/autogen-ext/src/autogen_ext/tools/mcp/_workbench.py:474 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/6f8250200f010317. Report an issue: GitHub.