fix: reject invalid dataplane tool schemas

Signed-off-by: lucarlig <luca.carlig@ibm.com>

Author: lucarlig

mcpgateway/services/dataplane_publisher.py

@@ -400,13 +400,17 @@ def _build_user_data(
         backend_items_by_server: BackendItemsByServer,
     ) -> dict[str, Any]:
         """Build already-filtered dataplane data for one user."""
+        visible_tools = [tool for tool in tool_rows if self._filter_for_user(tool, user_email, team_ids, is_admin=is_admin)]
+        for tool in visible_tools:
+            if not isinstance(tool.input_schema, dict):
+                raise ValueError(f"Tool {tool.id} has a non-object input schema")
+
         tool_by_id: dict[str, ToolMetadata] = {
             tool.id: {
                 "name": tool.original_name,
-                "input_schema": tool.input_schema if isinstance(tool.input_schema, dict) else {},
+                "input_schema": tool.input_schema,
             }
-            for tool in tool_rows
-            if self._filter_for_user(tool, user_email, team_ids, is_admin=is_admin)
+            for tool in visible_tools
         }
 
         return {

tests/unit/mcpgateway/services/test_dataplane_publisher.py

@@ -226,7 +226,7 @@ async def test_full_payload_generation_with_mock_db():
     tool2.id = "t2"
     tool2.name = "gw1-private_tool"
     tool2.original_name = "private_tool"
-    tool2.input_schema = None
+    tool2.input_schema = {}
     tool2.owner_email = "user1@example.com"
     tool2.team_id = "team1"
     tool2.visibility = "private"
@@ -338,6 +338,18 @@ async def test_full_payload_generation_with_mock_db():
         assert user3_backend["tool_schemas"] == {"public_tool": tool1.input_schema}
 
 
+def test_build_user_data_rejects_non_object_tool_schema():
+    """Dataplane snapshots fail closed when an enabled tool schema is malformed."""
+    from unittest.mock import Mock
+
+    from mcpgateway.services.dataplane_publisher import DataplanePublisherService
+
+    tool = Mock(id="bad-tool", original_name="bad", input_schema=None, visibility="public")
+
+    with pytest.raises(ValueError, match="Tool bad-tool has a non-object input schema"):
+        DataplanePublisherService()._build_user_data("user@example.com", set(), False, [], [], [], [], [tool], {})
+
+
 # ============================================================================
 # Edge Cases
 # ============================================================================