Website migration QA for AI agents

MCP Setup

Point your agent at the MCP endpoint

A stateless Streamable HTTP endpoint at https://app.difficat.com/mcp. Tools: discover_pages, capture_screenshot, start_comparison, get_comparison, get_report, get_screenshot, cancel_comparison.

Claude Code

claude mcp add --transport http difficat https://app.difficat.com/mcp

Generic mcpServers config

{
  "mcpServers": {
    "difficat": { "type": "http", "url": "https://app.difficat.com/mcp" }
  }
}

First Call

One request, a 402, then a paid retry

Every paid route answers an unauthenticated request with HTTP 402 and a payment challenge. Pay it and retry the same request to get the result.

Unpaid: see the challenge

curl -i https://app.difficat.com/api/v1/screenshots \
  -X POST -H 'Content-Type: application/json' \
  -d '{"url":"https://example.com"}'

# HTTP/1.1 402 Payment Required
# WWW-Authenticate: Payment ...

Paid: the same call through mppx

npx mppx@0.9 https://app.difficat.com/api/v1/screenshots \
  -X POST -H 'Content-Type: application/json' \
  -d '{"url":"https://example.com"}'

mppx handles the 402 automatically: it signs a USDC payment on Base and retries the request with the credential attached. See the OpenAPI document for every route and its request body.

Pricing

Paid per call, in USDC on Base

No account, no subscription, no minimum. Status, report and screenshot reads are free.

Call	Price	Notes
POST /api/v1/discover	$0.05 per call	Page discovery for a site
POST /api/v1/screenshots	$0.02 per call	Full-page screenshot of one URL
POST /api/v1/jobs	$0.02 per page	Reserved upfront for maxPages, no refund for unused pages — call discover first and set maxPages to the page count
GET /api/v1/jobs/{id}, /report, /files/{filename}	Free	Status, report and screenshot reads

A 50-page comparison job is $1.00 at today's price. Live prices are always in the OpenAPI document as x-payment-info on each paid operation.

Get USDC on Base

Fund your agent's wallet

Production accepts USDC on Base mainnet only. The cheapest way to try it is one screenshot call, $0.02.

1. Get USDC on any exchange or wallet that supports Base.
2. Withdraw or send it on the Base network — not Ethereum mainnet — to your agent's wallet address.
3. Keep a few dollars there. A 50-page comparison job is about $1.00 at today's price.
4. Point your agent's MPP or x402 client at that wallet and make your first call above.

Reference

Machine-readable docs

• OpenAPI document — every route, request/response schema, and live x-payment-info pricing
• MCP Registry entry — com.difficat/difficat in the official MCP Registry
• x402 Bazaar listing — the three paid REST routes in Coinbase’s x402 Bazaar
• llms.txt — a plain-text summary of DiffiCat and the agent API for AI assistants