USDC Payment Verifier on Base (x402 Proof of Payment)

Before your AI agent delivers a file, an answer or a service, check that the USDC payment it was promised really landed. Give a transaction hash and what you expect; get a clear verdict.

What it does

• Verify a payment (payments): reads the transaction on Base (or Base Sepolia) from public RPC nodes, decodes the Transfer events of the official Circle USDC contract, and checks:

  • the transaction succeeded,
  • USDC went to the expected recipient (to) and, optionally, from the expected payer (from),
  • the amount is at least min_amount,
  • it has at least min_confirmations.

  Verdicts: valid, mismatch, failed_tx, no_usdc_transfer, insufficient_confirmations, pending. The output also lists every USDC transfer in the transaction, the block time and the method used (transfer, or transferWithAuthorization / EIP-3009, the call x402 facilitators use to settle).

• Read a balance (balances): the current USDC balance of an address.

Read-only: no wallet, no key, no funds held, nothing is ever sent.

Pricing (pay per event)

Unknown transaction hash, invalid input or RPC outage: never charged. No start fee.

Example

Input:

{"payments": [{"tx_hash": "0x4699c8e64627e085a11b8bdd1097f576e1363c1e11731005d1eb0c296df93d80", "to": "0x17cd53c04d707ef0dd615ef56c633f02915a7905", "min_amount": 0.05}]}

Output (shortened, real values):

{"endpoint": "verify_usdc_payment", "ok": true, "result": {"verdict": "valid", "matched_amount": 0.05, "settlement_method": "transferWithAuthorization (EIP-3009, x402-style)", "checks": {"tx_succeeded": true, "recipient_matches": true, "amount_ok": true, "confirmations_ok": true}}, "charged_event": "verify-usdc-payment"}

Limits (honest)

• Base mainnet and Base Sepolia only; USDC only (no ETH or other tokens).
• Relies on public RPC nodes (rate limits possible; outages are not charged).
• A valid verdict says the payment matches; it says nothing about who the payer is (combine with a sanctions screening of the address if needed).

Sources

• Base public RPC (mainnet.base.org, sepolia.base.org), dRPC public fallback.
• Circle USDC contract addresses: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 (Base), 0x036CbD53842c5426634e7929541eC2318f3dCF7e (Base Sepolia).