MCP x402 — Evidence-Backed Web Verification for AI Agents

Verify a seller, product, offer, policy, or claim before an agent acts

Give an AI agent a public HTTP(S) page and 1 to 10 concrete conditions. The verificar_condicoes tool returns an evidence-based decision for every condition:

• confirmado — the page clearly supports the condition.

• rejeitado — the page clearly contradicts the condition.

• incerto — the available page evidence is insufficient.

Each verification includes the final source URL, page title, timestamp, condition-by-condition explanation, quoted evidence when available, a unique verificationId, and a SHA-256 pageHash.

Designed for

• AI purchasing and procurement agents;

• seller, product and offer verification;

• pre-purchase due diligence;

• policy and terms checking;

• commercial automation that requires evidence before taking action.

Simple x402 integration

• Free preflight validation before payment.

• $0.05 USDC per verification on Base mainnet.

• No account or subscription required.

• Available through MCP and HTTP.

• Ready-to-run buyer included in this repository.

• Coinbase x402 validation passed and Bazaar discovery enabled.

Live endpoints

• MCP: https://mcp-x402-production.up.railway.app/mcp

• Free verification preflight: POST https://mcp-x402-production.up.railway.app/preflight/verify-conditions

• Paid verification: POST https://mcp-x402-production.up.railway.app/verify-conditions

• Health: GET https://mcp-x402-production.up.railway.app/health

The service also provides paid public URL analysis and general AI consultation through analisar_url and consultar_ia.

Related MCP server: Pylon MCP Server

Live Service

• Base URL: https://mcp-x402-production.up.railway.app

• Health check: GET /health

• MCP endpoint: POST /mcp

• Paid URL analysis: POST /analyze

• Price: $0.05 USDC per paid request

• Network: Base mainnet (eip155:8453)

Production Status

• Production deployment active on Railway

• x402 version 2 payment flow

• Base mainnet payments (eip155:8453)

• Coinbase x402 validation passed

• Simulation accepted with HTTP 402

• Bazaar discovery metadata enabled

• Coinbase index active

MCP Tools

Decision verification

verificar_condicoes — $0.05 USDC

A paid decision-verification tool for agents.

Give it a public URL and one or more concrete conditions. It returns a decision based only on evidence extracted from that page:

• confirmado — the page clearly proves the condition.

• rejeitado — the page clearly contradicts the condition.

• incerto — the page does not provide enough evidence.

Each result includes the final source URL, page title, verification timestamp, condition-by-condition explanation, and a short quoted proof where available.

Example conditions:

• “The page identifies the seller.”

• “The product is available in Portugal.”

• “The page shows a price in euros.”

• “The document states that the service supports x402.”

This is designed for agents that need an evidence-based decision before taking the next action.

Technology

• Node.js and TypeScript

• Express

• Model Context Protocol

• OpenAI Responses API

• x402 payments

• viem

• Cheerio

• Railway

Security

• HTTPS provided by Railway

• Helmet security headers

• Rate limit of 100 requests per 15 minutes

• Structured request logs with unique request IDs

• Host validation and Railway health-check support

• Restricted OpenAI API key with access only to /v1/responses

• Environment files and secrets excluded from Git

Environment Variables

Server

Local Buyer

Example local .env.test file:

EVM_PRIVATE_KEY=your_private_key_here

Local Development

Install dependencies:

npm install

Start the development server:

npm run dev

Build the project:

npm run build

Start the compiled server:

npm start

Health Check

The health endpoint is public and does not require payment:

curl https://mcp-x402-production.up.railway.app/health

Ready-to-Run x402 Buyer

The repository includes ready-to-run buyers for applications and AI agents. The MCP buyer connects to the live service, validates the x402 payment requirements against Base mainnet USDC and a maximum payment of $0.05, signs the payment, retries the same tool call, and prints the settlement receipt and result.

Clone and prepare the buyer:

git clone https://github.com/Diogoup26/mcp-x402.git
cd mcp-x402
npm install

Create a local .env.test file in the project root:

EVM_PRIVATE_KEY=0xYOUR_64_HEX_CHARACTER_PRIVATE_KEY

Never commit .env.test or expose the private key.

Build the project:

npm run build

The following commands authorize real x402 payments on Base mainnet:

• consultar_ia: $0.02 USDC

• analisar_url: $0.05 USDC

• verificar_condicoes: $0.05 USDC

HTTP URL Analysis

npm run analyze -- "https://example.com" "Summarize this page."

HTTP Decision Verification

npm run verify -- "https://example.com" "The page identifies the seller."

MCP URL Analysis

npm run mcp:analyze -- "https://example.com" "Summarize this page."

MCP AI Consultation

npm run mcp:consult -- "Reply only with: MCP OK"

MCP Decision Verification

npm run mcp:verify -- "https://example.com" "The page identifies the seller."

A successful MCP payment prints:

• PAGAMENTO MCP: success

• the settlement receipt

• the tool response

The MCP buyer never prints the private key and rejects any payment that:

• is not on Base mainnet;

• does not use the configured Base USDC contract;

• exceeds $0.05 USDC.

Deployment

The main branch is connected to Railway. Every successful push triggers a new deployment. Railway uses:

npm run build
npm start

The deployment health-check path is /health.

License

ISC