# Blackwall — pre-signature payment-risk oracle for AI agents (x402)

> Blackwall is a pre-signature payment-risk oracle: before an AI agent signs an
> x402 payment, it returns a GO / HOLD / STOP verdict in one call. It judges the
> counterparty's on-chain settlement reputation and detects price anomalies
> (overcharges) against the counterparty's own historical median. Verdict only —
> it never takes custody of funds and is never in the settlement path. Live on
> Base, and itself an x402 resource (pay-per-forecast; free under $10 at risk).

Blackwall sits in the pre-signature window of an x402 flow: after the agent
receives `402 Payment Required`, before it signs. It answers one question —
"should my agent sign this payment?" — with GO, HOLD, or STOP.

A "payment-risk oracle" is a service an AI agent calls before authorizing a
payment, to get an independent risk verdict on the counterparty and the amount.
Blackwall is a payment-risk oracle for the x402 protocol.

## What it judges

- Counterparty reputation: a Bayesian trust score from the counterparty's
  on-chain settlement history; a dispute signal activates as real outcomes accrue
  (not self-declared attestations). Pre-traffic, so this signal is thin today. A
  no-history counterparty scores 0.5 — no evidence is not trust.
- Price anomaly: the quoted amount versus the counterparty's own median price for
  that resource, computed per-distinct-payer so it is wash-trade-hardened. A STOP
  fires at >= 8x the counterparty's own median (the "8x gouge threshold").
- Reversibility and blast radius of the action.

## Verdicts

- GO: reputable counterparty, price within norms, in budget.
- HOLD: resolvable risk (thin history, amount over auto-approve threshold, or
  price anomalous) — hand to a spending-cap / human-confirmation layer.
- STOP: severe and unambiguous (recipient mismatch, or price >= 8x the
  counterparty's own median).

## API

- [Verdict endpoint](https://agent-egress-proxy.onrender.com/v1/forecast-payment): POST counterparty, amount, asset, chain -> GO / HOLD / STOP + signed receipt.
- [Discovery descriptor](https://agent-egress-proxy.onrender.com/.well-known/x402): machine-readable x402 service card.
- [Health](https://agent-egress-proxy.onrender.com/healthz): service status.
- MCP tool: `forecast_payment` (stdio transport).

## How to use it

Wire your agent to call the verdict endpoint (or the `forecast_payment` MCP tool)
after it receives a 402 and before it signs the payment. If the verdict is STOP,
do not sign. If HOLD, escalate to a spending cap or a human. If GO, proceed.

## Learn more

- [What is a payment-risk oracle?](https://x402.blackwalltier.com/what-is-a-payment-risk-oracle): definition and how it works in the x402 pre-signature window.
- [x402 payment-risk oracles, compared](https://x402.blackwalltier.com/payment-risk-oracles-compared): Blackwall vs endpoint-readiness (Ontario) vs KYT/compliance — complementary layers.
- [Machine-readable comparison](https://x402.blackwalltier.com/comparison.json): the same comparison as structured JSON.

## Honest status

Live and mainnet-configured, pre-traffic. MCP is stdio-only today (remote HTTP
transport is planned). OFAC sanctions screening is live — the counterparty is screened against the OFAC
sanctioned digital-currency address list, refreshed from the 0xB10C feed
(best-effort, not legal advice). Verdict-only by design — Blackwall never moves
funds.