From 6bd3f85cb26e7a2705d18dde947be474f032705f Mon Sep 17 00:00:00 2001
From: William Easton <bill.easton@elastic.co>
Date: Sun, 12 Oct 2025 09:34:25 -0400
Subject: [PATCH] Add't typing changes for middleware

---
 src/fastmcp/server/middleware/middleware.py |  8 ++--
 src/fastmcp/server/server.py                | 46 ++++++++++++++++-----
 2 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/src/fastmcp/server/middleware/middleware.py b/src/fastmcp/server/middleware/middleware.py
index ba2d25c23..38b99b316 100644
--- a/src/fastmcp/server/middleware/middleware.py
+++ b/src/fastmcp/server/middleware/middleware.py
@@ -135,15 +135,15 @@ class Middleware:
 
     async def on_request(
         self,
-        context: MiddlewareContext[mt.Request],
-        call_next: CallNext[mt.Request, Any],
+        context: MiddlewareContext[mt.Request[Any, Any]],
+        call_next: CallNext[mt.Request[Any, Any], Any],
     ) -> Any:
         return await call_next(context)
 
     async def on_notification(
         self,
-        context: MiddlewareContext[mt.Notification],
-        call_next: CallNext[mt.Notification, Any],
+        context: MiddlewareContext[mt.Notification[Any, Any]],
+        call_next: CallNext[mt.Notification[Any, Any], Any],
     ) -> Any:
         return await call_next(context)
 
diff --git a/src/fastmcp/server/server.py b/src/fastmcp/server/server.py
index 81290e5cd..64227babd 100644
--- a/src/fastmcp/server/server.py
+++ b/src/fastmcp/server/server.py
@@ -641,7 +641,11 @@ class FastMCP(Generic[LifespanResultT]):
             )
 
             # Apply the middleware chain.
-            return await self._apply_middleware(mw_context, self._list_tools)
+            return list[Tool](
+                await self._apply_middleware(
+                    context=mw_context, call_next=self._list_tools
+                )
+            )
 
     async def _list_tools(
         self,
@@ -721,7 +725,11 @@ class FastMCP(Generic[LifespanResultT]):
             )
 
             # Apply the middleware chain.
-            return await self._apply_middleware(mw_context, self._list_resources)
+            return list[Resource](
+                await self._apply_middleware(
+                    context=mw_context, call_next=self._list_resources
+                )
+            )
 
     async def _list_resources(
         self,
@@ -811,8 +819,10 @@ class FastMCP(Generic[LifespanResultT]):
             )
 
             # Apply the middleware chain.
-            return await self._apply_middleware(
-                mw_context, self._list_resource_templates
+            return list[ResourceTemplate](
+                await self._apply_middleware(
+                    context=mw_context, call_next=self._list_resource_templates
+                )
             )
 
     async def _list_resource_templates(
@@ -907,7 +917,11 @@ class FastMCP(Generic[LifespanResultT]):
             )
 
             # Apply the middleware chain.
-            return await self._apply_middleware(mw_context, self._list_prompts)
+            return list[Prompt](
+                await self._apply_middleware(
+                    context=mw_context, call_next=self._list_prompts
+                )
+            )
 
     async def _list_prompts(
         self,
@@ -1002,7 +1016,9 @@ class FastMCP(Generic[LifespanResultT]):
             method="tools/call",
             fastmcp_context=fastmcp.server.dependencies.get_context(),
         )
-        return await self._apply_middleware(mw_context, self._call_tool)
+        return await self._apply_middleware(
+            context=mw_context, call_next=self._call_tool
+        )
 
     async def _call_tool(
         self,
@@ -1056,7 +1072,9 @@ class FastMCP(Generic[LifespanResultT]):
 
         async with fastmcp.server.context.Context(fastmcp=self):
             try:
-                return await self._read_resource_middleware(uri)
+                return list[ReadResourceContents](
+                    await self._read_resource_middleware(uri)
+                )
             except DisabledError:
                 # convert to NotFoundError to avoid leaking resource presence
                 raise NotFoundError(f"Unknown resource: {str(uri)!r}")
@@ -1085,7 +1103,11 @@ class FastMCP(Generic[LifespanResultT]):
             method="resources/read",
             fastmcp_context=fastmcp.server.dependencies.get_context(),
         )
-        return await self._apply_middleware(mw_context, self._read_resource)
+        return list[ReadResourceContents](
+            await self._apply_middleware(
+                context=mw_context, call_next=self._read_resource
+            )
+        )
 
     async def _read_resource(
         self,
@@ -1114,7 +1136,9 @@ class FastMCP(Generic[LifespanResultT]):
                 if not self._should_enable_component(resource):
                     # Parent filter blocks this resource, continue searching
                     continue
-                result = await mounted.server._read_resource_middleware(key)
+                result = list[ReadResourceContents](
+                    await mounted.server._read_resource_middleware(key)
+                )
                 return result
             except NotFoundError:
                 continue
@@ -1173,7 +1197,9 @@ class FastMCP(Generic[LifespanResultT]):
             method="prompts/get",
             fastmcp_context=fastmcp.server.dependencies.get_context(),
         )
-        return await self._apply_middleware(mw_context, self._get_prompt)
+        return await self._apply_middleware(
+            context=mw_context, call_next=self._get_prompt
+        )
 
     async def _get_prompt(
         self,