Sentinel Payment Preflights

Read-only stdio MCP server with two deterministic free preflights for public payment metadata, plus Sentinel Recovery's public service catalog and quote-request contract.

Source version 0.3.0 adds a pinned x402 v2 exact-EVM EIP-3009 safety profile. Checksummed versioned MCPB artifacts are published on the GitHub Releases page. It is not published to npm. The official MCP Registry name is io.github.TerminallyLazy/sentinel-recovery-services; verify the current mcp/server.json, release checksum, and Registry record before relying on a published version. The GitHub Pages site is static and is not a remote MCP endpoint.

Tools

• preflight_agent_payment_boundary analyzes one or two inline public JSON, Markdown, or text documents, with a 100 KiB combined limit.
• It performs 11 fixed checks covering request-versus-payment authority, payer policy, inbound versus outbound wallet authority, custody/signing/spending, the canonical payment tuple, quote expiry, replay handling, receipt states, sensitive wallet inputs, donation separation, and metadata integrity.
• Findings are deterministic clear, ambiguous, or missing results with a bounded locator, normalized evidence marker, risk, and correction. Supplied prose is never copied into model-visible output.
• It does not fetch requester-controlled URLs, execute document content, submit a request, connect a wallet, or move funds.
• clear means the required recognized structured declarations are present and no unmodeled supplied content was observed; it is not a certification and does not verify implementation behavior. For every check that can clear, an unknown field or non-allowlisted free-form value conservatively downgrades the declaration to ambiguous instead of guessing whether it is safe. External digest URLs remain ambiguous because the offline preflight does not fetch or trust them; the full review can verify supplied integrity evidence separately.
• preflight_x402_v2_payment_required analyzes exactly one decoded inline JSON x402 v2 PaymentRequired object using nine fixed checks. It accepts only the pinned closed-world Sentinel profile: exact, canonical eip155:<chain-id>, EIP-3009 transfer metadata, 1–64 unique complete alternatives, positive uint256 atomic amounts, and a 1–86,400 second timeout.
• The x402 profile is intentionally stricter than core x402. A structurally clear result does not prove that a chain exists, a token behaves as claimed, an EIP-712 domain is correct, a recipient controls an address, payer policy authorizes a payment, a signature is valid, settlement occurred, or a receipt exists. Permit2, ERC-7710, nonempty extensions, and other unmodeled content are reported as unsupported or ambiguous, not silently accepted.

Resources

• sentinel://services/catalog reads and validates the live services.json.
• sentinel://services/quote-request-contract reads and validates the live service-request.json.

A resource read or preflight moves no funds. It submits no quote request, authorizes no payment, and creates no service entitlement. The server never requests credentials, keys, signatures, wallet connections, custody, or wallet control. An optional $49 review is quote-first; using the free tool does not create a payment obligation.

Install and verify

From the repository root:

npm ci --prefix mcp --ignore-scripts
npm test --prefix mcp
npm audit --prefix mcp --audit-level=high
npm run pack:check --prefix mcp

Client configuration

Replace the example path with the absolute path to the verified checkout:

{
  "mcpServers": {
    "sentinel-recovery-services": {
      "command": "node",
      "args": ["/absolute/path/to/sentinel-recovery-support/mcp/server.mjs"]
    }
  }
}

The client launches node mcp/server.mjs over stdio. The server writes only MCP protocol messages to stdout; startup failures go to stderr.

Network and validation boundaries

• Only the two hard-coded canonical HTTPS URLs are fetched.
• Both preflight tools accept inline content only and make no network requests.
• JSON with duplicate object keys is rejected before evaluation; recognized fields and containers must match their bounded types and value domains.
• Requests use GET, a ten-second timeout, and a 256 KiB response cap.
• Responses must be JSON objects matching the expected minimal contract shape.
• An upstream failure returns an actionable MCP error with the canonical URL.
• No environment variables, API keys, install scripts, or wallet access are required.

The package is UNLICENSED because this repository does not currently publish a general code license. Installing or running the source does not grant any financial authority.