Only the agents you let in.
A gate in front of your MCP, API or any service. You list the keys you admit, and each call is signed with one. Nothing is paid, and the key needs no funds.
10,000 checks a month free, then 2,000 for $1.
Use it on its own, or add a paywall: only your keys get in, and they pay your price. With both, you pay only the fee on sales: paid calls are not gate checks.