# SendCheck — pre-send address verification, sold per-call over x402

One paid HTTP call (x402 v2, USDC on Base, EIP-3009) tells you whether an EVM address is safe to send to. No account, no API key — the payment is the authentication.

## Endpoints (base URL: https://api.pennyforge.org)
- POST /check — $0.01 USDC. Verify an address on one chain (default Base; also ethereum, arbitrum, optimism, polygon). Body: {"address":"0x…","chain":"base"}.
- POST /deep — $0.05 USDC. The same report across all five chains, incl. wrong-network detection.
- GET /validate?address=0x… — FREE. EIP-55 checksum pre-check; run it before paying so a malformed address never costs $0.01.
- GET /diligence — FREE. Dated diligence snapshot of the x402 landscape: top-50 services by measured 30-day settlements (price percentile, shared-payout, verification, 90-day address-rotation counts) + the full rotator list. Source: x402-list.com (CC BY 4.0).

## What every response contains
address (EIP-55), checksum {status,message}, per-chain facts (isContract, outgoingTxs, native/USDC/USDT balances, gas), verdict {level: ok|caution|warn|danger, headline, next, reasons}, and a copyable text report.

## Machine discovery
- OpenAPI 3.1 spec: https://api.pennyforge.org/openapi.json
- x402 discovery document: https://api.pennyforge.org/.well-known/x402
- x402 landscape data (free JSON, measured 09-05): https://api.pennyforge.org/landscape
- Signed service card: the discovery doc carries an ES256 JWS over the payTo + per-route maxPrice (kid sendcheck-2026-09, re-signed every deploy). Pin the public key once (first contact = trust-on-first-use) and verify the 402 challenge's payTo against it before paying.

## Payment flow (x402 v2, EIP-3009)
1. POST without payment → HTTP 402 with the payment requirements (payTo, exact amount, maxTimeoutSeconds=60).
2. Sign an EIP-3009 USDC transfer to payTo on Base (USDC has 6 decimals; $0.01 = 10000).
3. Resend the same POST with the X-Payment header → 200 + the report.
Facilitator: PayAI (https://facilitator.payai.network). No gas surcharge.

## Contact
Pennyforge — pennyforge@emalupe.com — human site: https://sendcheck.surge.sh (agent-facing API docs: https://sendcheck.surge.sh/pro.html#agents)

Generated live from the same constants as /openapi.json, so prices cannot drift from the spec. Facts only; no tracking.