diff --git a/slop_with_models.py b/slop_with_models.py
index 30d8de1..8c73633 100644
--- a/slop_with_models.py
+++ b/slop_with_models.py
@@ -119,7 +119,7 @@ tools = {
         "arguments": [
             { "name": "expression", "type": "str", "description": "the math expression to evaluate."}
         ],
-        "execute": lambda params: {"result": expr(params["expression"])},
+        "execute": lambda params: {"result": expr.evaluate((params["expression"])},
     },
     "greet": {
         "id": "greet",