modelcontextprotocol / modelcontextprotocol/python-sdk

support logging to stderr in Jupyter Notebook Environments.

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bug good first issue P3 ready for work
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Descripción

Is your feature request related to a problem? Please describe.
I want to make mcp python-sdk jupyter notebook compatible. When running in a notebook environment, MCP work but do not output stderr as it does normally.

For instance in jupyter notebook:

import mcp
import os
from mcp.client.stdio import stdio_client

serverparams = mcp.StdioServerParameters(
    command="uv",
    args=["--quiet", "run", "../src/echo.py"],
    env={"UV_PYTHON": "3.12", **os.environ},
)

async with stdio_client(serverparams) as (read, write):
    async with mcp.ClientSession(read, write) as session:
        await session.initialize()
        tools = await session.list_tools()
        print(tools)

Outputs:

meta=None nextCursor=None tools=[Tool(name='echo_tool', description='Echo the input text\n\n    Args:\n        text (str): The text to echo\n\n    Returns:\n        str: The echoed text\n    ', inputSchema={'properties': {'text': {'title': 'Text', 'type': 'string'}}, 'required': ['text'], 'title': 'echo_toolArguments', 'type': 'object'})]

while running the server without jupyter notebook:

❯ uv run --quiet src/echo.py
starting echo server

stderr is correctly displayed.

This is a big problem mostly because if the server is crashing or the command is wrong you have no way to know what's wrong: nothing is logged and the jupyter notebook cell just hangs.

Describe the solution you'd like
I found the culprit being the use of:

process = await anyio.open_process(
        [server.command, *server.args],
        env=server.env if server.env is not None else get_default_environment(),
        stderr=sys.stderr,
 )

In particular sys.stderr here is not working in the jupyter / ipython context. Instead I would suggest a working change as follow:

  1. remove the stderr params from the process and handle process.stderr in an async function as stdout / stdin is handled.
  2. to that effect, use a stderr_reader async function like the following:
    async def stderr_reader():
        assert process.stderr, "Opened process is missing stderr"
        try:
            async for line in process.stderr:
                if is_jupyter_notebook():
                    print(f"\033[91m {line.decode().strip()}")
                else:
                    # redirect to stderr as before
                    print(line.decode().strip(), file=sys.stderr)
        except anyio.ClosedResourceError:
            await anyio.lowlevel.checkpoint()

This would result in the same behavior as before while allowing the stderr to be logged in the jupyter notebook context.

Additional context
Jupyter notebook support support is also requested for mcpadapt which bring MCP server tools in any agentic framework, as many agentic framework demonstrate usage in jupyter notebooks.
https://github.com/grll/mcpadapt

Guía de contribución

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Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

Línea de trabajo

Comienza en stdio_client y en su llamada a anyio.open_process; después, compara cómo funciona el manejo existente de stdout y stdin con process.stderr. La tarea estará terminada cuando los errores del servidor sean visibles en los notebooks de Jupyter o IPython, mientras stderr conserve su comportamiento normal en cualquier otro lugar, incluso cuando el proceso falle o el comando no sea válido.

Escrito por el modelo de indexación a partir del texto del issue.

Evaluación

Stack tecnológico
jupyter-notebook, python
Área
backend, cli, developer-experience
Tipo de issue
Nueva funcionalidad
Dificultad
3/5
Tiempo estimado
1-2 días
Estado de actividad
Activo
Claridad
Bastante claro
Aptitud para principiantes
58/100

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