https://swagger.io/docs/specification/data-models/data-types/#readonly-writeonly

You can use the readOnly and writeOnly keywords to mark specific properties as read-only or write-only. This is useful, for example, when GET returns more properties than used in POST – you can use the same schema in both GET and POST and mark the extra properties as readOnly. readOnly properties are included in responses but not in requests, and writeOnly properties may be sent in requests but not in responses.
If a readOnly or writeOnly property is included in the required list, required affects just the relevant scope – responses only or requests only. That is, read-only required properties apply to responses only, and write-only required properties – to requests only.