diff --git a/lnschema_core/models.py b/lnschema_core/models.py
index 1873f150..ebda0c1a 100644
--- a/lnschema_core/models.py
+++ b/lnschema_core/models.py
@@ -2363,10 +2363,14 @@ def replace(
         pass
 
     def open(
-        self, is_run_input: bool | None = None
+        self, mode: str = "r", is_run_input: bool | None = None
     ) -> AnnDataAccessor | BackedAccessor | SOMACollection | SOMAExperiment:
         """Return a cloud-backed data object.
 
+        Args:
+            mode: can only be `"w"` (write mode) for `tiledbsoma` stores,
+                otherwise should be always `"r"` (read-only mode).
+
         Notes:
             For more info, see tutorial: :doc:`/arrays`.