I am not super familiar with the OpenAPI 3.1 specification, so please excuse me if I misunderstood anything. It appears that `tokenUrl`, a [fixed field](https://spec.openapis.org/oas/v3.1.1#fixed-fields-25), should have been modeled in the 3.1 JSONSchema as a `uri-reference` to [support relative urls](https://spec.openapis.org/oas/v3.1.1#relative-references-in-api-urls). REF: https://github.com/OAI/OpenAPI-Specification/blob/main/schemas/v3.1/schema.yaml#L899-L901 Note that the [3.0 schema](https://github.com/OAI/OpenAPI-Specification/blob/main/schemas/v3.0/schema.yaml#L938-L940) has the format as `uri-reference`, as I would expect. Happy to put in a pull request if this makes sense to someone with more experience in the repository. REL: https://github.com/seriousme/openapi-schema-validator/issues/178