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Blackwall X402 Guardrail
Pre-signature x402 payment verdict (GO/HOLD/STOP) for AI agents, with a verifiable signed receipt.
Quick Install
Automated & IDE SetupCopy the AI prompt to install this server into Claude Code, Cursor, or another agent — or use 1-click editor setup below.
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Manual Client & Custom JSON ConfigExpand JSON ▾
Install Config Generator
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💡 Paste into ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows)
Documentation Overview
Black_Wall remote MCP
A hosted remote MCP (Model Context Protocol over HTTP) that gives any MCP-capable agent a pre-signature payment-risk verdict — with no install and no signup. Add one URL and your agent can ask, before it signs an x402 payment, "should I pay this?" and get GO / HOLD / STOP — from counterparty settlement reputation, price-anomaly (quoted vs the payee's own median), and OFAC sanctions — plus a third-party-verifiable Ed25519 signed receipt.
Add it
Point your MCP client at:
Transport: Streamable HTTP. No API key. Verdicts for amounts under $10 at
risk are free; at or above that, the tool returns an x402 payment challenge
your agent settles from its own wallet (pass the settled payment back as an
X-PAYMENT header, then retry).
The tool: forecast_payment
| field | ||
|---|---|---|
counterparty | string, required | recipient wallet from the 402 |
amount | string, required | decimal string, e.g. "0.09" |
asset | string, required | e.g. USDC |
chain | string, required | e.g. base |
payer / resource / agent_id / context | optional | binds settlement / context |
Returns a verdict (GO/HOLD/STOP) + reasons + signals, and a
signed_receipt anyone can verify against the published key at
https://agent-egress-proxy.onrender.com/.well-known/blackwall-receipt-key.json
(any RFC 8032 Ed25519 library) — Black_Wall never has to be in the loop.
How it works
This Worker is a thin transport + proxy: it speaks minimal MCP JSON-RPC
(initialize / tools/list / tools/call / ping) and forwards
forecast_payment calls to the Black_Wall x402 oracle. All decision logic and
the receipt come from the oracle unchanged.
Fail-closed by design: if the oracle errors, is unreachable, or returns a
non-verdict, the tool returns an error — never a phantom GO. A payment
guardrail that can't reach its backend must not imply "safe to pay."
Registry
Published to the official MCP Registry as
com.blackwalltier/blackwall-x402-guardrail.
Develop
By BlueTier. Verdict only — never takes custody, never in the settlement path. No evidence is not trust.
Related MCP Servers
Frequently Asked Questions about Blackwall X402 Guardrail
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CategoryFinance & Fintech
5/5 checks healthy over the last 7h
37Quality signal: Fair · 37/100How this signal is calculated ▾
Server availabilityNot measured
Not scored for repo-hosted servers — we can't reach the running server, only its GitHub page. Hosted MCP endpoints are health-checked live.
Verified ownership10/20
Documentation & tools16/30
Adoption & activity2/15
Community engagement0/10
A guidance signal from public completeness & health data — not a user rating. New listings start lower and rise as they add docs, get verified, and grow adoption. Signals we can't observe for a listing are skipped, not counted against it.
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