fix: change Resource URI fields from AnyUrl to str (#1863)

src/mcp/server/fastmcp/resources/base.py

@@ -1,14 +1,12 @@
 """Base classes and interfaces for FastMCP resources."""
 
 import abc
-from typing import Annotated, Any
+from typing import Any
 
 from pydantic import (
-    AnyUrl,
     BaseModel,
     ConfigDict,
     Field,
-    UrlConstraints,
     ValidationInfo,
     field_validator,
 )
@@ -21,7 +19,7 @@ class Resource(BaseModel, abc.ABC):
 
     model_config = ConfigDict(validate_default=True)
 
-    uri: Annotated[AnyUrl, UrlConstraints(host_required=False)] = Field(default=..., description="URI of the resource")
+    uri: str = Field(default=..., description="URI of the resource")
     name: str | None = Field(description="Name of the resource", default=None)
     title: str | None = Field(description="Human-readable title of the resource", default=None)
     description: str | None = Field(description="Description of the resource", default=None)

src/mcp/server/fastmcp/resources/types.py

@@ -11,7 +11,7 @@ import anyio.to_thread
 import httpx
 import pydantic
 import pydantic_core
-from pydantic import AnyUrl, Field, ValidationInfo, validate_call
+from pydantic import Field, ValidationInfo, validate_call
 
 from mcp.server.fastmcp.resources.base import Resource
 from mcp.types import Annotations, Icon
@@ -94,7 +94,7 @@ class FunctionResource(Resource):
         fn = validate_call(fn)
 
         return cls(
-            uri=AnyUrl(uri),
+            uri=uri,
             name=func_name,
             title=title,
             description=description or fn.__doc__ or "",

src/mcp/server/lowlevel/server.py

@@ -79,7 +79,6 @@ from typing import Any, Generic, TypeAlias, cast
 import anyio
 import jsonschema
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
-from pydantic import AnyUrl
 from typing_extensions import TypeVar
 
 import mcp.types as types
@@ -337,7 +336,7 @@ class Server(Generic[LifespanResultT, RequestT]):
 
     def read_resource(self):
         def decorator(
-            func: Callable[[AnyUrl], Awaitable[str | bytes | Iterable[ReadResourceContents]]],
+            func: Callable[[str], Awaitable[str | bytes | Iterable[ReadResourceContents]]],
         ):
             logger.debug("Registering handler for ReadResourceRequest")
 
@@ -412,7 +411,7 @@ class Server(Generic[LifespanResultT, RequestT]):
         return decorator
 
     def subscribe_resource(self):  # pragma: no cover
-        def decorator(func: Callable[[AnyUrl], Awaitable[None]]):
+        def decorator(func: Callable[[str], Awaitable[None]]):
             logger.debug("Registering handler for SubscribeRequest")
 
             async def handler(req: types.SubscribeRequest):
@@ -425,7 +424,7 @@ class Server(Generic[LifespanResultT, RequestT]):
         return decorator
 
     def unsubscribe_resource(self):  # pragma: no cover
-        def decorator(func: Callable[[AnyUrl], Awaitable[None]]):
+        def decorator(func: Callable[[str], Awaitable[None]]):
             logger.debug("Registering handler for UnsubscribeRequest")
 
             async def handler(req: types.UnsubscribeRequest):

src/mcp/server/session.py

@@ -227,12 +227,12 @@ class ServerSession(
             related_request_id,
         )
 
-    async def send_resource_updated(self, uri: AnyUrl) -> None:  # pragma: no cover
+    async def send_resource_updated(self, uri: str | AnyUrl) -> None:  # pragma: no cover
         """Send a resource updated notification."""
         await self.send_notification(
             types.ServerNotification(
                 types.ResourceUpdatedNotification(
-                    params=types.ResourceUpdatedNotificationParams(uri=uri),
+                    params=types.ResourceUpdatedNotificationParams(uri=str(uri)),
                 )
             )
         )