Hello,
According to AORN's 2016 "Retained Surgical Items Prevention Checklist," instruments should be counted if you are entering a cavity (pelvic, thorax, or abdomen). Instrument counts should be performed if you can leave an instrument in the wound. Also, it should be performed if the possibility of extending the incision exists (going to full abdominal hysterectomy).
I know it's old school not to do an instrument count for vag hysts, but AORN recommendations do support the claim to count.
https://www.aorn.org/-/media/aorn/essentials/retained-surgical-items/files/policy-and-procedure_retainedsurgicalitems.docx