Do the commissions paid to contractors and brokers count as bribery from the perspective of Islamic economics, and is it permissible to mention the name of the agent company in the specifications if the contractor might import the material himself?

If contractors and brokers market your company's products to other companies, this is a legitimate brokerage. However, if they are employees in the companies you sell to, then giving them a percentage of the profit to buy from you is considered among the forbidden gifts to employees and a bribe, the giver and receiver of which are cursed. You are not required to put the name of the company that appointed you in the specifications booklet; what is required is to fulfill the mentioned specifications.