There is no single catalog of what agents can buy

Coinbase and Circle both publish open registries of x402 services, and they overlap by ten hosts. Build discovery on one and your agent cannot see most of the market.

What to do: Read both. Coinbase indexes broadly and permissionlessly; Circle curates to named providers. Treat either alone as a sample, not a census.

Coinbase: 14,668 endpoints across 1,533 hosts. Circle: 943 across 22. Just 44 identical resource URLs in common, measured 2026-08-06.