# MCP x402 – Evidence-Backed Web Verification [Verified] [Health: Active]

**Category:** 🔎 Search & Data Extraction  
**Repository:** https://github.com/Diogoup26/mcp-x402  
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**Directory Page:** https://allmcps.com/mcp/mcp-x402-evidence-backed-web-verification

## Description
Evidence-backed web verification for AI agents. Analyze public URLs and verify sellers, products, offers, policies, or claims against concrete conditions, with quoted evidence, source details, timestamps, hashes, and x402 pay-per-use payments on Base.

## Claude Desktop Quick Installation
Remote MCP endpoint (confidence: high). Install path detected from listing signals. Add as a URL/SSE server in your client:

```json
"mcpServers": {
  "mcp-x402-evidence-backed-web-verification": {
    "url": "https://mcp-x402-production.up.railway.app/mcp"
  }
}
```

## Documentation

## What MCP x402 – Evidence-Backed Web Verification does

MCP x402 – Evidence-Backed Web Verification evaluates information published on a public web page. An agent supplies an HTTP(S) URL and between one and ten concrete conditions, such as whether a seller is identified, a product is available in Portugal, a price is shown in euros, or a policy mentions a required service.

The result is reported per condition using three possible decisions: `confirmado` when the page clearly supports the condition, `rejeitado` when it clearly contradicts it, and `incerto` when the available page evidence is insufficient. Results include the final source URL, page title, verification time, an explanation for each condition, quoted proof when available, a unique `verificationId`, and a SHA-256 `pageHash`.

## How it works

The service can be reached through its public MCP endpoint or HTTP endpoints. Paid verification uses x402 version 2 payments on Base mainnet, identified by `eip155:8453`, with a listed price of $0.05 USDC per verification. A free preflight route validates the request before payment. The repository also includes a buyer that connects to the live service, checks the payment requirements against Base mainnet USDC and the maximum amount, signs the payment, retries the same call, and prints the settlement receipt and result.

The production service is deployed on Railway. Its public MCP endpoint is `https://mcp-x402-production.up.railway.app/mcp`; the service also exposes health, preflight, URL analysis, and paid verification routes. Bazaar discovery metadata is enabled on the paid HTTP and MCP surfaces.

MCP x402 – Evidence-Backed Web Verification is most relevant to procurement agents, seller and offer checks, pre-purchase due diligence, policy validation, and other workflows that require evidence before an action. It only evaluates evidence extracted from the supplied public page, so it is not a substitute for checking private systems or inaccessible sources.

## Setup and configuration

For local server development, the repository documents `npm install`, `npm run dev`, `npm run build`, and `npm start`. The server requires `OPENAI_API_KEY`; `OPENAI_MODEL` is optional and defaults to `gpt-5-mini`. `HOST` and `PORT` are optional, with documented defaults of `0.0.0.0` and `3000`. `PUBLIC_SERVICE_URL` can define the canonical public HTTPS origin, while Railway can supply `RAILWAY_PUBLIC_DOMAIN` automatically. `OBSERVABILITY_SALT` is recommended for pseudonymizing source and client fingerprints across restarts.

The included local buyer has separate wallet configuration. `EVM_PRIVATE_KEY` is required for the buyer to authorize Base mainnet payments, and `JOURNEY_ID` is optional. The private key should not be committed or exposed. Running the buyer commands can authorize real payments.

## Tools and capabilities

- `verificar_condicoes`: verifies one or more conditions against a public page for $0.05 USDC.
- `analisar_url`: fetches and analyzes a public HTTP or HTTPS page for $0.05 USDC.
- `consultar_ia`: sends a prompt to the OpenAI Responses API for $0.02 USDC.
- HTTP access through `/analyze` and `/verify-conditions`.
- Free health and preflight routes for service or request validation.
- Evidence metadata including source URL, title, timestamp, quoted proof, verification ID, and page hash.

## Limitations and notes

The verification input must be a public HTTP(S) page, and the conditions should be concrete. A page that does not contain enough evidence produces `incerto`; the system does not establish a condition merely because the page is relevant. Paid calls require USDC on Base mainnet, while local server execution requires an OpenAI project API key. The README documents a production deployment and live endpoints, but it does not claim confirmed CDP native MCP catalog indexing. Rate limiting is documented at 100 requests per 15 minutes.

_Full upstream README: https://allmcps.com/mcp/mcp-x402-evidence-backed-web-verification/readme_