The Farm and Ranch Contract (TXR 1701) has two sections on page 9 related to fees: a Ratification of Fee and an Agreement for Payment of Brokers’ Fees.
A listing broker who has already agreed to pay a commission to a cooperating broker—in the MLS, for example—should fill out the Ratification of Fee box. This authorizes the escrow agent to pay the cooperating broker from the listing broker’s fee at closing.
The seller and buyer should not sign the Agreement for Payment of Brokers’ Fees if the listing broker has already agreed to pay the cooperating broker’s commission elsewhere. This could bind the seller or buyer to pay additional amounts to the listing broker or the cooperating broker they didn’t intend.
However, a seller and buyer could sign the Agreement for Payment of Brokers’ Fees if the listing broker hasn’t offered to pay a commission, like if the property wasn’t listed in the MLS. Note that the agreement states either the seller or the buyer will pay the brokers.