An SD-JWT VC's issuer JWT carries vct (a case-sensitive credential type, never selectively disclosed), iss, iat, optional exp and nbf, cnf for holder key binding and status pointing to a token status list. The typ was changed from vc+sd-jwt to dc+sd-jwt in late 2024 to avoid a clash with the W3C VC media type; verifiers should require dc+sd-jwt.
Issuer keys are found through /.well-known/jwt-vc-issuer metadata, X.509 certificates in x5c, or out-of-band trust lists, and type metadata at the vct URL can describe display and claim rules. The format is used by the EU Digital Identity Wallet next to mdoc, presented with OpenID4VP. It is still a draft, so pin the version your ecosystem's profile names.