When I tried to use this API, there was a pattern where Schema did not exist.
https://developer.atlassian.com/cloud/jira/platform/rest/v3/api-group-issue-fields/#api-rest-api-3-field-search-get
Schema property does not exist for “id: parent”.
It used to be there, but has it changed recently?
At least it seems to work differently than API Reference.