Your classic checks looks like this if created from inside WATO.
globals().setdefault("custom_checks", [])
custom_checks = [
{
"id": "448cf5ed-6a42-4b4a-b7fc-05d61a2740c1",
"value": {
"service_description": "Statut Demo xxx",
"command_line": "$USER1$/check_http -S -H xxx.jaliosworkplace.com -u https://xxx.jaliosworkplace.com/plugins/SiteSettingsPlugin/front/loginRight.jsp",
"command_name": "check_http",
"has_perfdata": True,
},
"condition": {"host_name": ["xxx.test.net"]},
"options": {"disabled": False, "docu_url": "omdadmin"},
},
] + custom_checks