Your Planner Knows About Tools Your User Can't Call
A free-tier user opens your support chat and asks, "Can you issue a refund for order #4821?" Your agent replies, "I'm not able to issue refunds — that's a manager-only action. You could escalate via the dashboard, or I can transfer you." The refusal is correct. The ACL at the refund tool is correct. And you have just told an anonymous user that a tool named issue_refund exists, that it is gated by a role called manager, and that your platform accepts order IDs of the shape #NNNN.
Your planner knows about tools your user can't call. That asymmetry — full catalog visible to the reasoning layer, partial catalog executable at the action layer — is where most agent authorization gets quietly wrong. ABAC at the tool boundary catches the unauthorized invocation. It doesn't catch the capability disclosure that already happened one token earlier, in the plan, the refusal, or the "helpful" suggestion of a workaround.
