This structure is not valid. It should be:
"parameters": [
{
"name": "user_key",
"description": "Your access API Key",
"schema":

,
"in": "query",
"x-data-threescale-name": "user_keys",
"required": true
},
]

Reported by: jnyilimb

https://access.redhat.com/documentation/en-us/red_hat_3scale_api_management/2.13/html/providing_apis_in_the_developer_portal/how-to-write-an-openapi-document-for-use-as-a-threescale-openapi-spec_creating-a-new-service-based-on-oas#annotations:1ec26ceb-d94a-486d-9eb5-ec17149fc145