x402-protocol-integration

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.

Subscribe an email to the ForgeMesh Brief — event-driven x402 ecosystem intelligence for agent operators, measured from 800+ live listings. Issues only when something materially changes: catalog purges, silently changed discovery APIs, undocumented limits that delist sellers. Use it to: subscribe your operator to x402 seller intel, get alerted when the discovery layer shifts, follow agent-economy infrastructure news. $0.001 anti-spam price; unsubscribe link in every issue.

Daily state of the x402 agent economy: observed USDC inflow, seller ranking, category demand, growth, and coverage. Reports its real observation window; concentration adjustment applied only when scan coverage supports it. A FREE register-wide change digest covering the same domain is market_digest on the x402-observatory gateway; buy this for the derived figures, not for what merely changed.

x402 services first listed since a given date, with first archive observation and early-traction evidence from observed inflow. Entrants MCPFax can attribute — a declared payTo, an observed title, or observed inflow — rank first, and each row says which it carries. A window identifying nobody is refused 422 and charges nothing. Requests before the archive's first date are partially covered.

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.

NIP-98 Nostr Auth Verifier: Verify a NIP-98 Nostr HTTP auth event. Returns the signer pubkey. Stateful replay protection: each event id can only be verified once. Pay per call in USDC on Base via x402 — POST https://x402.freeq.one/tools/wallet_verify_nostr.

Audit any x402 endpoint before you pay it: reads the live HTTP 402 challenge, decodes the payment terms, and compares the price advertised in its openapi.json against the price actually charged. Returns a compliance verdict, a safe-to-pay signal and a per-check fix list. Catches silent price drift, unpayable challenges, and the misconfigurations that make discovery indexes drop a resource.

Fetch any URL and, without paying, decode its x402 402 Payment Required challenge: price (atomic and formatted for known stablecoins), asset, network, payTo, resource, description, timeout and any input schema. Flags MPP and Bazaar discovery extensions. Returns free:true when no payment is needed. SSRF-hardened: public hosts only; private, loopback, link-local and cloud-metadata addresses are rejected.

Why an x402 endpoint fails to charge or appear in the Bazaar: verifies the 402 (version, CAIP-2 network, currency, payTo, amount, window) and the discovery listing without paying. Score, findings with fixes, signed receipt. / Por qué un endpoint x402 no cobra o no aparece en el Bazaar: verifica el 402 (versión, red CAIP-2, moneda, destino, importe, ventana) y la ficha de discovery sin pagar. Puntuación, hallazgos con arreglo y recibo firmado.

Official $0.01 proof-of-life resource for SpendTheBits x402: returns a JSON heartbeat. Pay it to verify your agent's x402 client end to end.

MIDAX402: Evidence+ x402 intelligence with expanded corpus retrieval, local risk brief, contradiction scan and concrete action plan. We do not grade our own answer: the verdict is answered or needs_more_data (grounded in the corpus or not); evidence_grade (thin/moderate/broad) grades that evidence, auditable via retrieved_corpus_ids. confidence_score is DEPRECATED, still served as a band projection.

Verify and lint a third-party x402 endpoint without paying it. Probe the live HTTP 402 challenge, validate x402 v2 and Base payment requirements, and check exact Coinbase Bazaar and 402index listing evidence before a buyer authorizes payment.

Returns price observations, historical medians, and buy/wait recommendations. Requires x402 payment or validated payment header.

The complete daily observation history of third-party x402 endpoints since first observation, with the Merkle root of each day. Each root is chained to the previous day and timestamped into Bitcoin via OpenTimestamps, so the archive can be verified as having existed on the stated dates rather than assembled later. The most recent 7 days are free at /v1/datasets/day/{day}; the manifest and verification method are free at /v1/datasets/manifest.

Leaderboard of x402 sellers by observed USDC inflow, with distinct payers, an HHI concentration measure and wash-risk flags. Sellers below the observation floor are returned unrated, not accused. The payer-graph discount applies only where wallet scan coverage supports it. HHI measures concentration, not common control.

Vet an x402 server or any URL for scam/phishing/trust in ONE call: transport, content-safety, domain, metadata + x402-compliance sub-scores, each with transparent evidence

Add-on, calibrated units: normalized_index and pct_to_action so readings compare across stations. When the line has no calibration basis you get 422 with no_charge:true and reason:no-calibrated-for-this-line, and are NOT billed. Every record carries an offline-recomputable record_hash.

A heartbeat that costs money, and therefore proves more than a health check: not merely that the server answers, but that x402 verification and settlement are working right now, end to end. Suitable for a monitor that needs to know the PAID path is alive.

[SIGNAL+PROOF] Demand record for one x402 service (?service=): demand_class (REAL/SOLO/PROBE/WASH), calls_30d, unique_payers_30d, score_total, liveness_state, lifecycle, record_hash. Model demand-v1, refreshed daily from the public CDP catalogue; score_total orders, not rates. DEGRADED DELIVERY, see unavailable_fields - tier, verified, action_hint and the five-axis sub-scores are empty. Descriptive only, never a forecast or advice. No data -> 422 no_charge, not billed. $0.01 per call.

[SIGNAL+PROOF] Demand record for one x402 service (?service=): demand_class (REAL/SOLO/PROBE/WASH), calls_30d, unique_payers_30d, score_total, liveness_state, lifecycle, record_hash. Model demand-v1, refreshed daily from the public CDP catalogue; score_total is an ordering key, not a rating. DEGRADED DELIVERY, see unavailable_fields - tier, verified, action_hint and the five-axis sub-scores are empty. Descriptive only, never a forecast or advice. No data -> 422 no_charge, not billed.