Check the MCP contract your integration depends on.
Before you deploy, confirm that required tools still exist and see whether their input schemas changed. $0.10 USDC per paid check on eip155:8453. No subscription.
| Free preflight | Paid deployment check |
|---|---|
| Connection, protocol, tool names, schema health | All preflight checks, required-tool checks, per-tool schema fingerprints and baseline comparison |
| Compact point-in-time result | ALLOW / BLOCK / REVIEW, detailed evidence and payment-linked receipt |
1. Build your request
Enter a public Streamable HTTP MCP endpoint and the exact tools your integration uses.
{
"target_url": "https://your-server.example/mcp",
"required_tools": [
"search"
],
"check_profile": "basic"
}
Generating or downloading JSON stays in your browser. The free-check button sends only your endpoint URL to ProofRail. No wallet connection or payment.
2. See your free result now
Enter an endpoint above to check its current compatibility.
Call mcp_release_preflight with only target_url, or POST {"target_url":"YOUR_ENDPOINT"} as JSON to https://drkdm4jd-8767.uks1.devtunnels.ms/api/preflight.
3. Buy one deployment check
Use an x402-capable client to POST the generated JSON to https://drkdm4jd-8767.uks1.devtunnels.ms/api/certify, or call mcp_release_certify through an x402-compatible MCP client at https://drkdm4jd-8767.uks1.devtunnels.ms/mcp.
A plain browser or ordinary MCP connection does not pay automatically. The first HTTP call returns 402 and the PAYMENT-REQUIRED header. Your x402 client signs the displayed USDC authorization and retries the same request with PAYMENT-SIGNATURE. Check the price, network and recipient before authorizing.
Download the Node.js buyer: defaults to a free quote; payment requires --pay and your own wallet key. Install npm install @x402/core@2.27.0 @x402/evm@2.27.0 viem@2.57.0, save your JSON as request.json, then run node buy.mjs request.json. To authorize one $0.10 purchase, set PROOFRAIL_BUYER_KEY in your local environment and run node buy.mjs request.json --pay. Never paste a wallet key into this website.
Who should pay?
Use the paid check when an agent or release workflow depends on specific tools exposed by a remote MCP server and needs a reusable contract plus verifiable evidence. If you only need to see whether the endpoint connects, the free preflight is enough. For testing your own implementation against the MCP specification, the official conformance suite is a better fit.
4. Reuse the evidence on the next release
Save certification.evidence.contract_baseline from the paid response. On your next check, send that object as baseline_schema_hashes together with your required_tools.
- ALLOW: requested checks passed at observation time.
- BLOCK: a required tool disappeared, a schema is invalid, or another checked contract failed.
- REVIEW: a schema changed or evidence is incomplete. A changed hash alone does not prove incompatibility.
The response includes a verification_url for the settled receipt. Preserve the detailed response separately: the receipt binds its hashes, it is not the full report.
Point-in-time protocol and schema checks; not a security audit or uptime guarantee. Target tools are not executed unless an operator-configured safe fixture is explicitly selected. Up to 100 required tools and 100 baseline hashes per request.