diff --git a/src/langbot/pkg/utils/funcschema.py b/src/langbot/pkg/utils/funcschema.py
index f18b9e6b..bbe8b77b 100644
--- a/src/langbot/pkg/utils/funcschema.py
+++ b/src/langbot/pkg/utils/funcschema.py
@@ -83,7 +83,7 @@ def get_func_schema(function: typing.Callable) -> dict:
 
         parameters['properties'][param.name] = {
             'type': param_type,
-            'description': args_doc[param.name],
+            'description': args_doc.get(param.name, ''),
         }
 
         # add schema for array
diff --git a/tests/unit_tests/utils/test_funcschema.py b/tests/unit_tests/utils/test_funcschema.py
index 8df7ff07..66e31655 100644
--- a/tests/unit_tests/utils/test_funcschema.py
+++ b/tests/unit_tests/utils/test_funcschema.py
@@ -188,4 +188,22 @@ class TestGetFuncSchema:
 
         result = funcschema.get_func_schema(doc_func)
 
-        assert result['parameters']['properties']['param_name']['description'] == 'This is the param description.'
\ No newline at end of file
+        assert result['parameters']['properties']['param_name']['description'] == 'This is the param description.'
+
+    def test_missing_parameter_doc_uses_empty_description(self):
+        """Test that undocumented parameters do not crash schema generation."""
+        funcschema = get_funcschema_module()
+
+        def partially_documented_func(documented: str, undocumented: int):
+            """Function with one undocumented param.
+
+            Args:
+                documented: Documented parameter.
+            """
+            pass
+
+        result = funcschema.get_func_schema(partially_documented_func)
+
+        props = result['parameters']['properties']
+        assert props['documented']['description'] == 'Documented parameter.'
+        assert props['undocumented']['description'] == ''