Is an agent required to maintain any set of books of accounts?

Yes as per Rule 56(11) of the CGST Rules, 2017, every agent referred in section 2(5) of the CGST Act, 2017 shall maintain accounts containing:
1. particulars of authorization received by him from each principal to receive or supply goods or services on behalf of such principal separately;
2. particulars including description, value and quantity (wherever applicable) of goods or services received on behalf of every principal;
3. particulars including description, value and quantity (wherever applicable) of goods or services supplied on behalf of every principal;
4. details of accounts furnished to every principal; and
5. tax paid on receipts or on supply of goods or services effected on behalf of every principal.

(ICAI FAQ PUBLICATIONS 06-09-2017 ACCOUNTS AND RECORDS: FAQ NO. 4)