Depending on the setup, TIB will do a token exchange, it will trade the IDP token with a Tyk token using the gateway API, then give the end user the tyk token. The Tyk token is then checked for validity.
If this is OIDC, then you may want to leave TIB out altogether and just configure Tyk to use OIDC, then validity is checked against the IDP’s JWK set.
M.