What you are buying when you retain a search firm
Formally, you are buying access and assessment: candidates who are not looking, evaluated by people who assess leaders for a living. In practice you are also buying a set of constraints. Every retained firm carries off-limits obligations that place its existing clients' executives out of reach, and the larger the firm, the larger the blocked pool. You are also buying an allocation decision made inside the firm: whether your mandate gets the partner who pitched it or a researcher stretched across six searches. Neither constraint appears in the proposal, and both shape the shortlist more than the brand on the letterhead.