fix(mcp): move search/filters mutual exclusion check from schema to tool layer

Pydantic model_validators in ListRolesRequest and ListUsersRequest fired
during fastmcp parameter deserialization, producing a raw ToolError with
"1 validation error for call[list_roles]" text that the StructuredContent-
StripperMiddleware wrapped as non-JSON content. Tests that called
json.loads() on the result then raised JSONDecodeError instead of seeing
the expected error dict.

Removes the model_validators from both schemas and moves the mutual
exclusion check into the tool functions' try blocks, returning a proper
RoleError/UserError JSON object so tests can assert "error" in data.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: aminghadersohi

superset/mcp_service/role/schemas.py

@@ -28,7 +28,6 @@
     Field,
     field_validator,
     model_serializer,
-    model_validator,
     PositiveInt,
 )
 
@@ -184,17 +183,6 @@ def parse_columns(cls, v: Any) -> List[str]:
         """Accept JSON array, list, or comma-separated string."""
         return parse_json_or_list(v, "select_columns")
 
-    @model_validator(mode="after")
-    def validate_search_and_filters(self) -> "ListRolesRequest":
-        """Prevent using both search and filters simultaneously."""
-        if self.search and self.filters:
-            raise ValueError(
-                "Cannot use both 'search' and 'filters' parameters simultaneously. "
-                "Use either 'search' for text-based searching or 'filters' for "
-                "precise column-based filtering, but not both."
-            )
-        return self
-
 
 class RoleError(BaseModel):
     error: str = Field(..., description="Error message")

superset/mcp_service/role/tool/list_roles.py

@@ -76,6 +76,16 @@ async def list_roles(
     )
 
     try:
+        if request.search and request.filters:
+            return RoleError.create(
+                error=(
+                    "Cannot use both 'search' and 'filters' parameters simultaneously. "
+                    "Use either 'search' for text-based searching or 'filters' for "
+                    "precise column-based filtering, but not both."
+                ),
+                error_type="validation_error",
+            ).model_dump(mode="json")
+
         from superset.daos.role import RoleDAO
 
         def _serialize_role(obj: Any, cols: list[str] | None) -> RoleInfo | None:

superset/mcp_service/user/schemas.py

@@ -28,7 +28,6 @@
     Field,
     field_validator,
     model_serializer,
-    model_validator,
     PositiveInt,
 )
 
@@ -215,17 +214,6 @@ def parse_columns(cls, v: Any) -> List[str]:
         """Accept JSON array, list, or comma-separated string."""
         return parse_json_or_list(v, "select_columns")
 
-    @model_validator(mode="after")
-    def validate_search_and_filters(self) -> "ListUsersRequest":
-        """Prevent using both search and filters simultaneously."""
-        if self.search and self.filters:
-            raise ValueError(
-                "Cannot use both 'search' and 'filters' parameters simultaneously. "
-                "Use either 'search' for text-based searching or 'filters' for "
-                "precise column-based filtering, but not both."
-            )
-        return self
-
 
 class UserError(BaseModel):
     error: str = Field(..., description="Error message")

superset/mcp_service/user/tool/list_users.py

@@ -79,6 +79,16 @@ async def list_users(
     )
 
     try:
+        if request.search and request.filters:
+            return UserError.create(
+                error=(
+                    "Cannot use both 'search' and 'filters' parameters simultaneously. "
+                    "Use either 'search' for text-based searching or 'filters' for "
+                    "precise column-based filtering, but not both."
+                ),
+                error_type="validation_error",
+            ).model_dump(mode="json")
+
         from superset.daos.user import UserDAO
 
         can_view_sensitive = user_can_view_data_model_metadata()