Blackwall X402 Guardrail MCP Server

by blackwalltier Your server? Claim it

answering

Blackwall X402 Guardrail is answering right now. Last checked 8 min ago. It exposes 1 tools. Last commit 25 Aug 2026.

Keyless hosted MCP: pre-signature x402 payment verdict (GO/HOLD/STOP) with a signed receipt.

Uptime history 47 days of history

47 days agonow

100.0%

Uptime 24h

91 of 91 checks

Tools

read from the server

104 ms

Response time

average over 24h

Stars

last commit 25 Aug 2026

Nothing serious here today

Today is the operative word: we check Blackwall X402 Guardrail every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 8 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

claude mcp add blackwall-x402-guardrail --transport http https://mcp.blackwalltier.com

~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "blackwall-x402-guardrail": {
      "url": "https://mcp.blackwalltier.com"
    }
  }
}

~/.codex/config.toml

[mcp_servers.blackwall-x402-guardrail]
url = "https://mcp.blackwalltier.com"

.cursor/mcp.json

{
  "mcpServers": {
    "blackwall-x402-guardrail": {
      "url": "https://mcp.blackwalltier.com"
    }
  }
}

.vscode/mcp.json

{
  "mcpServers": {
    "blackwall-x402-guardrail": {
      "url": "https://mcp.blackwalltier.com"
    }
  }
}

Available tools 1

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

forecast

forecast_payment

Pre-signature x402 payment verdict: GO / HOLD / STOP for paying a counterparty, from settlement reputation, price-anomaly (quoted vs the payee's own median), and OFAC sanctions — with a third-party-verifiable Ed25519 signed receipt. Verdict only; never takes custody. Free under $10 at risk; over that, returns an x402 payment challenge.

Endpoints

URL	Transport	State	Latency	Checked
https://mcp.blackwalltier.com	streamable-http	answering	77 ms	8 min ago

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Blackwall X402 Guardrail — questions

Answers built from our own checks of this server.

What can Blackwall X402 Guardrail do?

It exposes 1 tools, read directly from the server on our last check. Among them: forecast_payment. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

Is Blackwall X402 Guardrail working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 104 ms. The bar chart above shows every period we have measured.

How do I connect Blackwall X402 Guardrail?

Copy the ready config from this page — we generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each with the file path that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.

Does Blackwall X402 Guardrail need an API key?

No. Blackwall X402 Guardrail completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 1 of them are readable on this page. This is what we observed, not what the docs claim.

How fast is Blackwall X402 Guardrail?

It answers our handshake in 104 ms on average, which is faster than 83% of all working MCP servers we measure. That puts it in the quick quarter of the ecosystem. The comparison comes from our own checks across the whole registry, every 15 minutes.

Is Blackwall X402 Guardrail open source?

We cannot say either way: written in JavaScript, 0 stars on GitHub and 2 open issues, but we could not determine the licence, and without one the code is not open source by default.