fix(mcp): validate field names in mcp_required_fields; surface backend error in submit UI

litellm/proxy/management_endpoints/mcp_management_endpoints.py

@@ -161,6 +161,10 @@ if MCP_AVAILABLE:
         _base_validate_and_normalize_mcp_server_payload(payload)
         _validate_mcp_server_name_fields(payload)
 
+    _VALID_MCP_REQUIRED_FIELDS: frozenset = frozenset(
+        NewMCPServerRequest.model_fields
+    )
+
     def _validate_mcp_required_fields(payload: Any) -> None:
         """Validate submission payload against admin-configured mcp_required_fields."""
         from litellm.proxy.proxy_server import (
@@ -173,6 +177,18 @@ if MCP_AVAILABLE:
         if not required_fields:
             return
 
+        # Fail fast on unknown field names — a typo in the config would silently
+        # block every submission with a confusing "missing fields" error.
+        unknown = [f for f in required_fields if f not in _VALID_MCP_REQUIRED_FIELDS]
+        if unknown:
+            raise HTTPException(
+                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                detail={
+                    "error": f"mcp_required_fields contains unknown field names: {unknown}. "
+                    "Check general_settings.mcp_required_fields in your proxy config."
+                },
+            )
+
         # Mirror the UI's compliance checks (MCPStandardsSettings.tsx FIELD_GROUPS):
         # auth_type requires a real value — "none" is treated as absent.
         _AUTH_TYPE_SENTINEL = "none"
@@ -750,7 +766,7 @@ if MCP_AVAILABLE:
             raise HTTPException(
                 status_code=status.HTTP_403_FORBIDDEN,
                 detail={
-                    "error": "Admin users should use POST /v1/mcp/server to create servers directly instead of the submission workflow."
+                    "error": "PROXY_ADMIN users should use POST /v1/mcp/server to create servers directly instead of the submission workflow."
                 },
             )
 

tests/test_litellm/proxy/management_endpoints/test_mcp_management_endpoints.py

@@ -1837,3 +1837,20 @@ class TestValidateMCPRequiredFields:
         with patch_proxy_general_settings({}):
             # Should not raise when no required fields are configured
             _validate_mcp_required_fields(payload)
+
+    def test_unknown_field_name_in_config_raises_500(self):
+        from litellm.proxy.management_endpoints.mcp_management_endpoints import (
+            _validate_mcp_required_fields,
+        )
+
+        payload = NewMCPServerRequest(
+            alias="My Server",
+            url="https://example.com/mcp",
+            transport=MCPTransport.sse,
+        )
+        # "source_Url" is a typo — not a real field on NewMCPServerRequest
+        with patch_proxy_general_settings({"mcp_required_fields": ["source_Url"]}):
+            with pytest.raises(HTTPException) as exc_info:
+                _validate_mcp_required_fields(payload)
+        assert exc_info.value.status_code == 500
+        assert "source_Url" in str(exc_info.value.detail)

ui/litellm-dashboard/src/components/mcp_tools/create_mcp_server.tsx

@@ -391,7 +391,10 @@ const CreateMCPServer: React.FC<CreateMCPServerProps> = ({
         onCreateSuccess(response);
       }
     } catch (error) {
-      NotificationsManager.fromBackend("Error creating MCP Server: " + error);
+      const reason = error instanceof Error ? error.message : String(error);
+      NotificationsManager.fromBackend(
+        isAdmin ? `Error creating MCP Server: ${reason}` : `Error submitting MCP Server: ${reason}`
+      );
     } finally {
       setIsLoading(false);
     }