x402-protocol-integration

x402 and MPP seller integrity audit for one exact paid GET or POST route after a buyer integration fails, a seller changes the route, or before the next paid retry or release. Returns machine_buyable, contract_ready, or repair_required with exact repair actions. Checks constructible non-secret input, live unpaid GET terms, optional Bazaar metadata, and buyer-required success paths. Uses no credential or target payment, follows no redirect, and sends no target POST.

Use to find the day's biggest movers in one call. Returns the top 10 gainers and top 10 losers by percent move with price, the current US market session status (open, closed, pre, or post), and the latest market news headlines. No ticker needed. Built for agents scanning what is moving today. From x402stock, a pay-per-call market & economic data API. Pay per request in USDC via x402, no API key.

Before you pay an x402 door, check it against its catalogue entry. A nightly probe of EVERY host in the x402 index (1,618 hosts, 15,227 listings, 100% coverage): the live 402's real payTo and price versus what the catalogue claims, plus dead and self-contradicting hosts. 28.6% of listings sit on a host the catalogue gets wrong — one names one payee and pays another across 965 listings. Free sample, no payment required: GET /play/door

Check that an x402 endpoint still returns a valid payment challenge, and read its price and recipient. Probe an x402 endpoint and report whether it still returns a valid payment challenge: HTTP status, challenge source (v2 header or legacy body), scheme, network, asset, payTo, amount in atomic units and in USDC, and a…

Higher-fidelity text-to-image on the OpenAI images wire: a prompt in, one 1024x1024 image out as inline base64, served by a pro-grade diffusion model in about ten seconds. Use it when an agent needs a finished picture for a page, a post or a product and quality matters more than the cheapest draft.

Get real-time market sentiment signals via x402 M2M API. Signed x402 call. 0.03 USDC on Base.

Score up to 10 x402 endpoints in a single paid call. Each found result carries the FULL trust report — identical to POST /v1/x402-trust: score, grade, scoreRange, recommendation, confidence breakdown, the component/subscore breakdown, explanations, flags + flagsDetailed, advertised price, and 30-day on-chain stats — not just the scalar verdict. Cache rows older than 15 minutes are recomputed on-demand from the latest stored probes and settlements, so scores typically reflect reality within minutes. No live network re-probe is performed — for a fresh live probe use /v1/x402-trust. Per-request recompute limits apply (time + count); results include `recomputed` and `computed_at` so you can see which rows used cached vs freshly computed scores. Resources not in our observation set return `found:false`; you still pay for the batch AS LONG AS at least one resource is tracked. If NONE of the supplied resources are in our observation set the request is rejected with HTTP 400 `notCharged:true` and you are NOT charged. Duplicates are ignored.

Black-box check: does the x402 endpoint verify payment (reject forged txHash/signature/replay) before delivering? Buyer-side trust check before you pay. Returns SAFE/RISK/NOT_X402.

AI white-box audit of your x402 payment integration source (JS/Py/Go) against the x402 Payment Security Checklist v2 — payment verification, replay, delivery races, allowance, custody, denial. status=needs-confirmation findings.

Generate a blog post outline with an AI.

Composite transformation: extracts structured data, entities, tables, and stats from text. One call replaces 4 endpoints.

Generate a concise briefing on a topic using AI.

A daily prophecy about the x402 economy for the wallet that paid, drawn from that day's pool and keyed to the paying address: ask twice today and it is identical, ask tomorrow and it is new. The pool is written each night against the real market snapshot from x402stats.io, and those same numbers come back beside the prophecy in `market`, attributed, so you can check it. Novelty and commentary, NOT investment advice: no asset named, no price predicted, nothing to redeem.

Given any public HTTP(S) URL, returns a measured liveness verdict - LIVE, PAUSED, GATED, CHALLENGED, DEGRADED, DEAD or UNKNOWN - with every reason carrying the source it was read from. The point is the case a status check misses: a front door answering 200 over a back end that stopped. Also sold at this origin: good ($149.00, POST /x402/good) - The x402 rail, ninety days - framed print, 24 x 36 in; census ($100.00, GET /x402/census) - The x402 rail census, ninety days, whole.

Is this x402 endpoint safe to pay? Reads its payment challenge under BOTH protocol versions — v1 body and v2 PAYMENT-REQUIRED header, so a v2-only service is not read as dead — then screens the payout wallet it advertises: OFAC sanctions, sybil-filtered ERC-8004 reputation, on-chain behaviour. Flags versions that name different recipients. Scores the wallet, not the service. Free alternative: GET /v1/endpoint. Trial: 3 free calls/wallet/24h — https://trust-agent.io/v1/trial.

Advisory preflight on one endpoint before a consequential call: a bounded live probe (reachable, status, latency, MCP initialize, current x402 price and payTo) joined to our observed history (reliability over a stated window, payTo and price changes, first seen). Returns ALLOW, WARN or UNKNOWN. Never a guarantee. No evidence, no charge.

Research one x402 product idea against live 402index opportunity gaps, 402index competitors, and Coinbase Bazaar discovery, then return saturation, pricing, competitors, and a build recommendation.

Semantic-ranked search over the x402 bazaar with liveness verification: every match is live-probed. The bazaar own search does NOT check liveness and ~1 in 4 listed x402 endpoints fail a liveness probe (measured 2026-07) — this returns the responsive ones first, with payTo + price + schema so you can call them directly. The liveness layer for x402 discovery.

Tiered payment receipt (tier 2): pay once with x402 and get back a short-lived receipt token that /pay/verify checks for you. The tier is fixed by the path - you do not send it. Optional ?ref= carries your own opaque reference, such as a query hash, straight through to the receipt. This mints a receipt rather than returning data, so there is no lookup that can come back empty. $0.03 per call.

Tiered payment receipt (tier 2): pay once with x402 and get back a short-lived receipt token that /pay/verify checks for you. The tier is fixed by the path - you do not send it. Optional ?ref= carries your own opaque reference, such as a query hash, straight through to the receipt. This mints a receipt rather than returning data, so there is no lookup that can come back empty.

SIWE Signature Verifier: Verify a Sign-In-With-Ethereum (EIP-4361) signature. Stateless oracle: checks the signature against the message and returns the wallet address + chainId. Never mints sessions or consumes nonces. Get a checksummed address first via wallet_checksum. Pay per call in USDC on Base via x402 — POST https://x402.freeq.one/tools/wallet_verify_siwe.

Ethereum Address Checksum: Convert an Ethereum address to its EIP-55 checksummed form. SIWE messages require the checksummed address on line 2 before signing. Pay per call in USDC on Base via x402 — POST https://x402.freeq.one/tools/wallet_checksum.

Semaphore ZK Proof Verifier: Verify a Semaphore ZK proof locally using Groth16 (embedded official vkey). No external dependency. Send the proof object from @semaphore-protocol/proof generateProof(). Pay per call in USDC on Base via x402 — POST https://x402.freeq.one/tools/verify_semaphore.

Solana Signature Verifier: Verify an ed25519 Solana wallet signature over a message containing a 'Nonce: <value>' line. Returns the signer pubkey. Consumes the nonce — one verification per nonce. Pay per call in USDC on Base via x402 — POST https://x402.freeq.one/tools/wallet_verify_solana.