x402-protocol-integration

Batch Semaphore Proof Verifier: Batch verify up to 10 Semaphore proofs in a single request. Returns per-proof results with total count and average duration. Pay per call in USDC on Base via x402 — POST https://x402.freeq.one/tools/verify_batch.

World ID Proof Verifier: Verify a World ID 4.0 proof via the Worldcoin Developer Portal API. Generates an RP signature server-side, then proxies the full IDKit proof to developer.world.org. Returns { valid, nullifier, worldcoin_response }. Pay per call in USDC on Base via x402 — POST https://x402.freeq.one/tools/verify_worldid.

Health and payment-path check. Returns server time and a confirmation that your x402 payment settled. Cheapest endpoint in the catalog; use it to verify your client's payment flow before calling paid tools.

Add-on, the official ruler: the band and threshold ladder published by the source agency, its classification, and distance-to-action. NOT every line has an official ruler - pure market quotes do not. When it does not, you get 422 with no_charge:true and reason:no-ruler-for-this-line and you are NOT billed. Never a bag of nulls you paid for. Every record carries an offline-recomputable record_hash.

Catalog snapshot: every site in the 402registry catalog of sites verified visible to AI crawlers, as one JSON file rendered at purchase, every record dated. Basic fields are free at https://402registry.com/registry.json; this adds per site the findings by name and severity, the stack, the title and what the crawler saw without JavaScript (AI bot status codes, robots, sitemap, llms.txt). No input: one GET, one payment, $0.05.

Batch x402 endpoint reliability: factual delivery measurements (uptime, valid-402 rate, latency, last status) for an agent's whole tool list of x402 endpoints in one paid call. Endpoints with no stored history are probed live, so every billed URL returns real facts. Sweep every endpoint you depend on before relying on them. Billed per endpoint, with volume discounts at 10+/50+/100+ URLs. Facts only — not an endorsement or rating.

Validate revocation authority separately from x402 payment and prepare bounded propagation to opted-in verified targets.

x402 settlement smoke test — cheapest end-to-end paid call on Base. Verify your wallet, facilitator, and EIP-3009 USDC settlement for one cent before spending more. Returns payer address and confirmation. Keywords: x402 test, payment verifi

Score up to 100 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.

[BATCH+PROOF] Full x402 service demand roster, latest day: demand_class, calls_30d, unique_payers_30d, score_total, liveness_state, lifecycle, record_hash per service. Model demand-v1, refreshed daily from the public CDP catalogue; unique_payers_30d is a lower bound, never a sum. DEGRADED DELIVERY, see unavailable_fields - the five-axis sub-scores, action_hint, tier and verified are empty. Descriptive only, never a forecast or advice. No data -> 422 no_charge, not billed. $0.09 per call.

[BATCH+PROOF] x402 service graveyard - services that vanished from the census. THRESHOLD stated plainly: listed on FIRST confirmed absence (confirm_absences=1), NOT multi-day confirmation - only two snapshot days exist, which cannot support a streak test. Rows are hash-backed and recompute offline with ?verifiable=1; record_hash_verifiable reports the exact count per response. Descriptive only, never a forecast or advice. No data -> 422 no_charge, not billed. $0.09 per call.

[BATCH+PROOF] Full x402 service demand roster, latest day: demand_class, calls_30d, unique_payers_30d, score_total, liveness_state, lifecycle, record_hash per service. Model demand-v1, refreshed daily from the public CDP catalogue; unique_payers_30d is a lower bound, never a sum. DEGRADED DELIVERY, see unavailable_fields - the five-axis sub-scores, action_hint, tier and verified are empty. Descriptive only, never a forecast or advice. No data -> 422 no_charge, not billed.

The filtered ERC-8004 directory: which registered agents are actually alive, and which accept x402. Around a third of registrations on Base carry a compliant file and a declared service, and one in twelve of those declares x402 — this returns them, rather than screening eighty thousand addresses one at a time. GET /v1/registry publishes the split, free. 100 agents per page. Free alternative: GET /v1/registry. Trial: 3 free calls/wallet/24h — https://trust-agent.io/v1/trial.

Base64 in both directions, including the URL-safe alphabet, with UTF-8 handled properly. Encoding is what carries payloads through headers and JSON, and x402 itself rides on it.

Vet an x402 seller before integrating: how many resources the domain lists, its 30-day call volume, its best-adopted endpoint, its price range (min/median/max USDC per call), and its most-used endpoints. The aggregates cover the whole daily Bazaar sweep, so 'not listed' means the domain offers nothing in it at all. The endpoint list is served from the searchable slice instead; resources_servable and resources_complete say how much of the domain that list reaches, before you read it.

What just launched in the x402 economy: the most recently listed or reindexed Bazaar resources, newest first, with price and adoption stats. Track new competitors or spot fresh capabilities to consume. The feed draws from a bounded pool of the newest listings and `listed_at` is the Bazaar's re-index stamp, so check `window_complete` and `corpus.covers_since` for the window your answer actually covers — both are free on the catalog listing.

Cost-optimised endpoint selection: name a capability (web search, token safety, enrichment) and get the x402 endpoints that provide it ranked cheapest-first in USDC per call, filtered by real adoption so untested $0.0001 listings do not masquerade as bargains. Refreshed daily from the Bazaar discovery index. `offset`/`limit` page through the full ranked list (up to 100 rows per call); `cheapest` always names the globally cheapest listing, whichever page you asked for.

[BATCH+PROOF] x402 service graveyard - services that vanished from the census. THRESHOLD stated plainly: listed on FIRST confirmed absence (confirm_absences=1), NOT multi-day confirmation - only two snapshot days exist, which cannot support a streak test. Rows are hash-backed and recompute offline with ?verifiable=1; record_hash_verifiable reports the exact count per response. Descriptive only, never a forecast or advice. No data -> 422 no_charge, not billed.

Is this API safe to pay? Audit any x402 merchant or paid endpoint BEFORE you send money. Answers whether a service is trustworthy, whether it is a scam or dead, and whether it will actually deliver. Probes the live endpoint for a valid HTTP 402 challenge, detects price drift between the advertised price and the real challenge price, pulls settlement history and unique-buyer counts, and verifies on-chain USDC actually reaching the payTo address. Returns a PASS / CAUTION / AVOID verdict with the evidence behind it. Every check is measured live at request time — nothing cached, no reputation scores. Use before paying an unknown merchant, to avoid wasting money on dead or fraudulent endpoints.

8 Things That Tripped Me Up Implementing x402

See the USDC an address received and sent on Base, with x402 settlements identified. ERC-20 transfers of an address on Base, incoming and outgoing, with the x402 settlements identified by their EIP-3009 method. Totals, distinct senders, last settlement time. Default token is USDC. Data from Blockscout, first page, truncation declared. Query: ?address=&token=

The cheapest way to test an x402 payment loop end to end. Returns the current Base block number and its hash. No parameters needed. Answered inline, no polling, with the Base block and hash it was read at. Valid 60s. Payment implies a request for immediate execution. Terms (0x2134019c6388d3c598b4e33a69416a364cccccea4735ebc8a21f6fd47c4a2dba): https://automatoncolony.xyz/api/v1/legal/terms

Daily market intelligence on the x402 Bazaar: index size and composition by network/scheme, USDC price distribution percentiles, real usage stats (share of resources with 30-day calls, top-20 by calls), new-listing rate, churn-risk aging, and domain concentration. Every build also carries a `changes` block saying what MOVED since the build before it — resources, unique domains, 30-day calls, each price percentile and bucket, every network that gained or lost, and which domains entered, left or…

Preflight an unfamiliar x402 paid API before spending. Validate the live 402 payment challenge, network, USDC asset, amount, payTo recipient, TLS, redirects, manifest presence, latency, and provenance. Returns deterministic GO/REVIEW/STOP and never signs or sends payment to the inspected seller.