Robert M. Gary wrote:
No, the AGI ticket includes the priv of signing off knowledge exams for
any FAA airmen certificate at the private or commercial level. The FAA
does not offer a fixed wing or rotor only ground instructor
certificate. It does not include the ability to sign off instrument
knowledge exams (that's just another test).

If you hold and AGII (Advance Ground Instructor - Instrument) then you
can sign off someone for the Instrument written.