McGriff makes it really easy - simple form that I have filled out with my information and just have to add the client's name, address, and email. Not usually important if you're working for homeowners or really small firms, but most contractors and larger architects have to have them for their own insurance audits. It's nothing more than proof of insurance, like showing your car insurance card to a rental car agent. The difference is that while you're on the hook for that car for a day or two, you're on the hook for that building for several years. So as a COI holder, they are entitled to updates in your coverage so they can ensure you're not in breach of contract (most big contracts have insurance requirements and that you maintain that coverage for a set amount of time.)
Named insured is common in the General Liability insurance world and is something we should understand if doing Design Build projects (there was a good article on it in a Structure edition recently), but Professional Liability is structured differently. If only they were suing themselves...they can still sue you, your insurance just won't foot the bill.