# `AshAuthentication.Oauth2Server.RefreshTokenResource.Verifier`
[🔗](https://github.com/team-alembic/ash_authentication_oauth2_server/blob/v0.1.0/lib/ash_authentication/oauth2_server/verifier.ex#L24)

Verifies the refresh-token resource has the shape the Token core
depends on:

  * `:id` attribute is writable (the library pre-allocates the new
    refresh row's id so a rotation is one filtered UPDATE).
  * `:rotate` action exists and carries a filter expression (filters
    already-rotated / already-revoked rows out of the underlying
    UPDATE; race-safety lives entirely here).

Violations raise at resource-compile time with a fix-it message.

---

*Consult [api-reference.md](api-reference.md) for complete listing*