ScrapeCheck MCP — Verify Scraped Web Data Against Reality

Verify what you scraped for the price of scraping it. This MCP server gives any agent a verification tool in its own toolbox: send a source URL, the scraped field values, and what was asked — ScrapeCheck re-fetches the page itself and returns an ed25519-signed verdict: pass, fail, or unverifiable.

Endpoint: https://scrapecheck-mcp.fly.dev/mcp (streamable HTTP) Payment: x402 in-band (USDC on Base) — no API key, no signup. A free allowance per client identity is served before payment is required.

Tools

Tool	Price	What it certifies
verify_web_field	$0.01	Full verification: value present on the re-fetched live page, served live, and an independent LLM judge confirms it answers what was asked. Positive verdict: pass.
verify_presence	$0.002	Presence only — does NOT confirm the value answers the question. Positive verdict: present, never pass.
get_verifier_info	free	The trust artifact: public key, benchmark summary, scope, endpoints.

The trust guarantee is structural, not statistical

A claim is never certified unless ScrapeCheck independently re-fetches the page and finds the claimed value there itself — and the judge's vote is mechanically voided if its restatement of the claim doesn't match what was actually claimed. Absence cannot pass, and substitution cannot pass. Anything unconfirmed — a skipped check, a failed fetch, a judge that errors — returns unverifiable, never pass.

Corroborated by benchmark (full verification only): 0 false passes across 67 frozen labeled cases (26 held out from all calibration, including adversarial traps where the claimed value appears on the page as the wrong thing), and 0 false passes across 21 live-web cases including 9 adversarial traps. Small-N corroboration of the structural guards — not a population accuracy claim.

Why trust this server's own claims?

Because you don't have to. Every verdict is ed25519-signed over canonical sorted-key JSON of all fields except signature; the public key is served at /pubkey and in-band via get_verifier_info; and every verdict carries an engine digest identifying exactly which prompt+calibration produced it. Verify offline — no need to trust the transport, the storefront, or us.

Live, unfiltered run stats — misses included: scrapecheck.fly.dev/stats. A verifier that only shows its passes isn't showing anything.

Payment flow (x402 in-band)

Standard @x402/mcp v2 flow: an unpaid call past the free allowance returns a PaymentRequired challenge in the tool result; pay with any x402 v2 client (e.g. wrapMCPClientWithPaymentFromConfig from @x402/mcp with an EVM signer) and the retried call returns the verdict plus the on-chain settlement in _meta["x402/payment-response"]. A refused or failed payment never yields a verdict, and a verdict that fails to produce never settles — you are charged only for completed work.

Integrator notes

• The full signed verdict object is in structuredContent on the wire (and byte-identical as JSON in content[0].text). Note: @x402/mcp's paying-client convenience result forwards content only — parse content[0].text there, or read structuredContent with a plain MCP client.
• Input contract (frozen): { url, claim, asked } — claim is an object of field values, e.g. {"price": "£51.77", "in_stock": true}.
• Scope (v1): server-rendered pages. Client-rendered (JS-only) content returns unverifiable — never a false fail, never a false pass.
• The same engine is also sold as a raw x402 HTTP API (https://scrapecheck.fly.dev/verify) and as the Scrape QA Apify actor for batch dataset verification. One engine, one signing key, one durable log.

Verify a verdict yourself (offline)

This repo ships a zero-dependency verifier — check any ScrapeCheck verdict without trusting us, the transport, or this server:

node tools/verify-verdict.mjs examples/verdict.json --pubkey key.json

Omit --pubkey to fetch the current key from /pubkey; pass it (an ed25519:… string or a saved /pubkey response) to verify fully offline. examples/verdict.json is a real production verdict — alter any field and verification fails. A verdict is valid iff its ed25519 signature verifies over the canonical (recursively key-sorted) JSON of every field except signature. MIT licensed — vendor the ~40 relevant lines into your own pipeline freely.

About this repository

This repo contains the thin MCP storefront only — transport, payment handling, and tool registration. The verification engine (the anchored re-fetch, the lenses, the judge, the signing key, and the benchmark fixtures) runs at the ScrapeCheck origin and is not part of this codebase.