com.blackwalltier/blackwall-x402-guardrail
Keyless hosted MCP: pre-signature x402 payment verdict (GO/HOLD/STOP) with a signed receipt.
Install
Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).
claude mcp add --transport http blackwall-x402-guardrail 'https://mcp.blackwalltier.com'{
"mcpServers": {
"blackwall-x402-guardrail": {
"type": "http",
"url": "https://mcp.blackwalltier.com"
}
}
}Documentation
From the project's README on GitHub, refreshed weekly. Links open on GitHub.
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:
https://mcp.blackwalltier.comTransport: 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
node test.mjs # unit tests (mocked oracle)
npx wrangler dev # run locally
npx wrangler deploy # deploy (Cloudflare Workers)By BlueTier. Verdict only — never takes custody, never in the settlement path. No evidence is not trust.
Frequently asked questions
What is com.blackwalltier/blackwall-x402-guardrail?
Keyless hosted MCP: pre-signature x402 payment verdict (GO/HOLD/STOP) with a signed receipt.
How do I install com.blackwalltier/blackwall-x402-guardrail?
It runs as a remote server. In Claude Code: claude mcp add --transport http blackwall-x402-guardrail 'https://mcp.blackwalltier.com'. For other clients, paste the JSON configuration from this page into their MCP settings.
Does com.blackwalltier/blackwall-x402-guardrail need an API key?
Its registry entry lists no required key or secret. Some features may still need an account with the service it connects to.
Is com.blackwalltier/blackwall-x402-guardrail open source?
Its code is public on GitHub, but the repository does not declare a standard license.
Who maintains com.blackwalltier/blackwall-x402-guardrail?
It is published by bluetieroperations-create. AI.tn lists it but does not maintain or endorse it.
From the official MCP Registry. Listing is not an endorsement: review a server's code and permissions before giving it access to your data.