drf_publish_list_mcp_tool() breaks GET requests to DRF ListAPIView

[gustahrodrigues]

Description:
I'm experiencing an issue when using drf_publish_list_mcp_tool() from django-mcp-server to expose a DRF ListAPIView. After wrapping my view with this function, direct GET requests to the API endpoint no longer work as expected.

Setup:

• Django==4.2.23
• djangorestframework (DRF)==3.15.1
• django-mcp-server==0.5.6
• uvicorn[standard]==0.35.0
• Python 3.10

Code Example:
my_app/views.py:

from rest_framework.generics import ListAPIView
from rest_framework import serializers

class MyStaticDataSerializer(serializers.Serializer):
    id = serializers.IntegerField()
    name = serializers.CharField()

class MyStaticDataListAPIView(ListAPIView):
    serializer_class = MyStaticDataSerializer
    permission_classes = []

    def get_queryset(self):
        return [
            {"id": 1, "name": "Alice"},
            {"id": 2, "name": "Bob"},
        ]

my_app/mcp.py:

from mcp_server import drf_publish_list_mcp_tool
from my_app.views import MyStaticDataListAPIView

# Everything works if I comment the section below
drf_publish_list_mcp_tool(
    MyStaticDataListAPIView,
    name="list_my_static_data_api_view",
    instructions="API view to list static data objects.",
)

validate_mcp.py

from mcp.client.streamable_http import streamablehttp_client
from mcp import ClientSession

async def main():
    async with streamablehttp_client("http://localhost:8000/mcp") as (
        read_stream,
        write_stream,
        _,
    ):
        async with ClientSession(read_stream, write_stream) as session:
            await session.initialize()
            tool_result = await session.call_tool("list_my_static_data_api_view")
            print(tool_result)

if __name__ == "__main__":
    import asyncio
    asyncio.run(main())

settings.py

...
INSTALLED_APPS = [
    "rest_framework",
    "mcp_server",
    "django.contrib.admin",
    "django.contrib.auth",
    "django.contrib.contenttypes",
    "django.contrib.sessions",
    "django.contrib.messages",
    "django.contrib.staticfiles",
]
...
...
MIDDLEWARE = [
    "django.middleware.security.SecurityMiddleware",
    "django.middleware.common.CommonMiddleware",
    "django.contrib.sessions.middleware.SessionMiddleware",
    "django.middleware.csrf.CsrfViewMiddleware",
    "django.contrib.auth.middleware.AuthenticationMiddleware",
    "django.contrib.messages.middleware.MessageMiddleware",
    "mozilla_django_oidc.middleware.SessionRefresh",
]
...

asgi.py

import os
from django.core.asgi import get_asgi_application

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'my_project.settings')
application = get_asgi_application()

Startup command: uvicorn my_project.asgi:application --host 0.0.0.0 --port 8000 --reload

Problem:
After using drf_publish_list_mcp_tool() to wrap my MyStaticDataListAPIView, direct GET requests to the endpoint (e.g., http://localhost:8000/my-app/my-static-data/) result in errors. The view works as expected before wrapping it with drf_publish_list_mcp_tool().

Stack trace:

INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)
INFO:     Started server process [8]
INFO:     Waiting for application startup.
INFO:     ASGI 'lifespan' protocol appears unsupported.
INFO:     Application startup complete.
[error    ] Internal Server Error: /my-app/my-static-data/ [django.request] dd.env= dd.service= dd.span_id=0 dd.trace_id=0 dd.version= request=<ASGIRequest: GET '/my-app/my-static-data/'> span_id=0 status_code=500 trace_id=0
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/asgiref/sync.py", line 489, in thread_handler
    raise exc_info[1]
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/exception.py", line 42, in inner
    response = await get_response(request)
  File "/usr/local/lib/python3.10/site-packages/django/core/handlers/base.py", line 253, in _get_response_async
    response = await wrapped_callback(
  File "/usr/local/lib/python3.10/site-packages/asgiref/sync.py", line 439, in __call__
    ret = await asyncio.shield(exec_coro)
  File "/usr/local/lib/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/local/lib/python3.10/site-packages/asgiref/sync.py", line 493, in thread_handler
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/sentry_sdk/integrations/django/views.py", line 94, in sentry_wrapped_callback
    return callback(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/views/decorators/csrf.py", line 56, in wrapper_view
    return view_func(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/django/views/generic/base.py", line 105, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/rest_framework/views.py", line 498, in dispatch
    request = self.initialize_request(request, *args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/mcp_server/djangomcp.py", line 489, in _patched_initialize_request
    original_request = request.original_request
AttributeError: 'ASGIRequest' object has no attribute 'original_request'

Expected Behavior:
Wrapping a DRF ListAPIView with drf_publish_list_mcp_tool() should not interfere with the standard GET behavior of the view.

Actual Behavior:
GET requests to the endpoint fail or return unexpected results after wrapping the view.

Steps to Reproduce:

1. Create a simple ListAPIView as above.
2. Make a GET request to the endpoint.

$ curl http://localhost:8000/my-app/my-static-data/
[{"id":1,"name":"Alice"},{"id":2,"name":"Bob"}]

4. Register it with drf_publish_list_mcp_tool().
5. Make another GET request to the endpoint and observe the error or unexpected response.

$ curl http://localhost:8000/my-app/my-static-data/
< Django error shown above> 

Relates to PR #27

Request:
Please advise if this is a known issue or if there is a recommended way to expose DRF list views to MCP without breaking their standard API behavior.

[richardscholtens]

You did not specify the parameter action in the drf_publish_list_mcp_tool function. Try this first:

from mcp_server import drf_publish_list_mcp_tool
from my_app.views import MyStaticDataListAPIView

drf_publish_list_mcp_tool(
    MyStaticDataListAPIView,
    name="list_my_static_data_api_view",
    instructions="API view to list static data objects.",
    actions={"get": "list"},
)

[gustahrodrigues]

You did not specify the parameter action in the drf_publish_list_mcp_tool function. Try this first:

from mcp_server import drf_publish_list_mcp_tool
from my_app.views import MyStaticDataListAPIView

drf_publish_list_mcp_tool(
MyStaticDataListAPIView,
name="list_my_static_data_api_view",
instructions="API view to list static data objects.",
actions={"get": "list"},
)

In order to try it, I have to do the following changes:

# views.py
-class MyStaticDataListAPIView(ListAPIView):
+class MyStaticDataListAPIView(GenericViewSet, ListModelMixin):

#urls.py
-    path("my-static-data/", views.MyStaticDataListAPIView.as_view(), name="my-static-data"),
+    path("my-static-data/", views.MyStaticDataListAPIView.as_view({'get': 'list'}), name="my-static-data"),

#mpc.py
 drf_publish_list_mcp_tool(
     MyStaticDataListAPIView,
     name="list_my_static_data_api_view",
-    instructions="API view to list static data.",
+    instructions="API view to list static data objects.",
+    actions={"get": "list"},
 )

Even with those changes, I got the same error while running $ curl http://localhost:8000/my-app/my-static-data/.

To be clear, validate_mcp.py is functioning correctly in both implementations.

[Artui]

You did not specify the parameter action in the drf_publish_list_mcp_tool function. Try this first:

from mcp_server import drf_publish_list_mcp_tool
from my_app.views import MyStaticDataListAPIView

drf_publish_list_mcp_tool(
    MyStaticDataListAPIView,
    name="list_my_static_data_api_view",
    instructions="API view to list static data objects.",
    actions={"get": "list"},
)

Actions are needed for Viewsets, but this is a ListAPIView, so those are not needed in the example.

I think Django's ASGI request handling is different from WSGI (which is what this library relies on). I'll check what changes are needed to support it

[richardscholtens]

Ah, my bad. I only worked with the viewsets until now.

[zacharypodbela]

I'm experiencing the exact same issue but with WSGIRequest instead of ASGIRequest:

AttributeError: 'WSGIRequest' object has no attribute 'original_request'

Root Cause

In BaseAPIViewCallerTool.__init__() at line 501, the framework is patching both normal API calls and MCP calls with the additional logic:

def __init__(self, view_class, **kwargs):
    view_class.initialize_request = self._patched_initialize_request  # <- This
    self.view = view_class.as_view(**kwargs)

The patched method expects all requests to have an original_request attribute, but only MCP requests have this - regular HTTP requests use standard Django request objects without it:

@staticmethod
def _patched_initialize_request(self, request, *args, **kwargs):
    original_request = request.original_request  # <- This
    original_request.request = request
    original_request.method = request.method
    return original_request

Just a thought: Why are we even patching this in the first place? Django is pretty opinionated about using composition and inheritance. I can work on a PR that fixes the issue and refactors this to be more in line with those principles.

[zacharypodbela]

Here's a PR that fixes this issue: #40

[omarbenhamid]

Thanks @zacharypodbela for the PR, seems a good one.

@gustahrodrigues could you confirm that solves your problem ?