Top up · USDC on Base

Top up credits

Self-serve credit top-up for API keys, paid in USDC on Base. Bind a paying wallet, then the service credits newly observed USDC transfers idempotently.

See pricing →
Live · GET /balance · /usage

Check your balance

Paste your API key to read current credits, total spent, and recent ledger events. Read-only — your key is sent only to numproof.com.

Calls GET /balance and GET /usage with your Bearer key.
balance
Ready.
Flow

How top-up works

  1. Register a wallet. POST /topup/register binds the paying wallet address to your API key.
  2. Send USDC on Base. Transfer USDC to the address returned by registration.
  3. Claim the transfer. POST /topup/claim credits newly observed transfers idempotently — re-claiming never double-counts.

The current credit value per USDC is exposed in signup, top-up, and x402 discovery responses.

Settlement asset
USD Coin (USDC) on Base
0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
Non-HTTPS, private, loopback, and unresolved webhook targets are rejected before billing. Top-up requires an API key.