refactor(base.py): simplify type of Union fields to the first type in the Union

fix(test_agents_template.py): set value of list field to an empty list
fix(test_llms_template.py): change type of 'request_timeout' field to float

tests/test_agents_template.py

@@ -48,6 +48,7 @@ def test_zero_shot_agent(client: TestClient):
         "type": "Tool",
         "list": True,
         "advanced": False,
+        "value": [],
     }