letter to consulate

[srian]

My husband is sponsoring for my parents visa and my parents have their interview in about 9 days. My husband has sent the "letter to consulate" using basic format and no where he has mentioned in the letter stating reaons why his in-laws would go back to India. Is this a must as i have already sent the documents to my parents. My parents would carry afidavit of assurance of return ( combined for both of them) in which they would mention the reasons as why they would come back from USA. Please advice if it was required for my husband as well to mention the reasons in his letter to consulate?

Also only my husband has signed in the letter to consulate, was it required for me ( daughter of applicants) also to sign in the letter to consulate?

Thanks