fix(auth): normalize empty optional client metadata URIs

Author: Mrutunjay Kinagi

src/mcp/shared/auth.py

@@ -68,6 +68,13 @@ class OAuthClientMetadata(BaseModel):
     software_id: str | None = None
     software_version: str | None = None
 
+    @field_validator("client_uri", "logo_uri", "tos_uri", "policy_uri", "jwks_uri", mode="before")
+    @classmethod
+    def normalize_empty_optional_uris(cls, v: Any) -> Any:
+        if v == "":
+            return None
+        return v
+
     def validate_scope(self, requested_scope: str | None) -> list[str] | None:
         if requested_scope is None:
             return None

tests/client/test_auth.py

@@ -83,6 +83,23 @@ def valid_tokens():
     )
 
 
+def test_oauth_client_metadata_treats_empty_optional_uris_as_none():
+    metadata = OAuthClientMetadata(
+        redirect_uris=[AnyUrl("http://localhost:3030/callback")],
+        client_uri="",
+        logo_uri="",
+        tos_uri="",
+        policy_uri="",
+        jwks_uri="",
+    )
+
+    assert metadata.client_uri is None
+    assert metadata.logo_uri is None
+    assert metadata.tos_uri is None
+    assert metadata.policy_uri is None
+    assert metadata.jwks_uri is None
+
+
 @pytest.fixture
 def oauth_provider(client_metadata: OAuthClientMetadata, mock_storage: MockTokenStorage):
     async def redirect_handler(url: str) -> None: