Is authority letter required when dropping off documents for h1b visa drop off via a representative?

Hi I have a drop off appointment in a few days. I am planning to send my brother for it. Is an authority letter required? I know it is required for pick up, but is it required for drop off as well? Also can someone point me to the authority letter format required for pick up?

Thanks!

The person dropping off will need a government ID. You can write a general letter addressed to the VAC, stating that you are authorizing so and so to drop off your visa application documents. Provide the DS-160 reference no. in the letter and sign.

https://www.ustraveldocs.com/in/en/general-information#faqs

Can someone else, such as a friend or a travel agent, drop off my Interview waiver application on my behalf?

Yes. You can designate a representative to drop-off your interview waiver application on your behalf. Be sure to provide them with all the necessary documents required for your Interview waiver application. Your appointment letter has a checklist.