I think that the individual that work with Customs Brokerage Services can be called a 'broker', not that he/she can´t be called 'agent' (my level of English don´t allow me to confirm or deny it with a hundred percent certainty).
My opinion is based in the job description (below)
Let´s the experts butt in the thread, then.
Customs Brokerage Services
Need to clear customs fast? Our experienced technical experts can help your goods clear quickly and efficiently with our electronic customs-clearance network. How? By taking advantage of the latest Customs release initiatives and reviewing your goods to make sure they comply with product-specific regulations.
We realize that international trade issues can be challenging. Our customs experts can guide you through the complexity of:
Specific product requirements
It is true that Customs is moving towards post-entry verification and audits. This means all importers and exporters must keep accurate trade data. We'll review your records to ensure they comply with both tariff and non-tariff-based requirements, and we'll make sure you're prepared for a potential Customs audit.
As an approved agent of the Department of Foreign Affairs and International Trade ( DFAIT ), we can handle all your import and export permit requirements for controlled goods. We'll give you advice on any product requirements or non-tariff barriers.