Register an API endpoint that will accept x402 micropayments. Returns a payment address and asset details to advertise in 402 responses.
API key (pk_test_* or pk_live_), JWT session, agent token (agent_), Ed25519 session (sess_), or portal token (portal_).
1 - 2551 - 500^\/GET, POST, PUT, DELETE, PATCH, ANY 0.0001 < x <= 9999991000USDC, EURC Endpoint registered