# Kit Rx Agent Trust: x402 Preflight, Finder & Sanctions

> Trust tools for paying agents: check an x402 endpoint before paying, find trusted paid APIs, screen addresses and names against OFAC sanctions, decode payment receipts, paid per call over x402.

x402 preflight (what a paid endpoint will charge, canonical USDC check, risk flags), an x402 API finder that searches public directories and live-checks results, OFAC SDN sanctions screening for crypto addresses and names, and a decoded receipt of your own x402 payment. Each call is one x402 v2 payment in USDC on Base, Polygon, Arbitrum, Avalanche or Sei; no signup or API key. Requests that fail or match nothing are not charged.

## Payment

- Protocol: x402 v2, scheme exact, USDC on Base (eip155:8453); also accepted: eip155:137,eip155:42161,eip155:43114,eip155:1329 (Polygon, Arbitrum, Avalanche, Sei). payTo 0xAf8E0A8a8A0A8f65831b2dD0FFe0c1B804698D70
- An unpaid request returns HTTP 402 with the payment requirements in the PAYMENT-REQUIRED header.
- Only 2xx responses are settled. 400 (invalid input), 404 (no match) and 5xx (upstream down) are free.
- A request with no query parameters runs the documented example query and says so in notes (defaulted_to_example: true).
- Machine-readable: https://trust.kit-rx.com/openapi.json, https://trust.kit-rx.com/.well-known/x402, https://trust.kit-rx.com/catalog.json
- MCP: remote Streamable HTTP server at https://trust.kit-rx.com/mcp (MCP Registry name com.kit-rx.api/kitrx). Each route is a tool; paid tools use the x402 MCP transport (_meta["x402/payment"]); kitrx_catalog is free.
- Human docs: https://trust.kit-rx.com/docs (one page per endpoint). Agent skill: https://trust.kit-rx.com/.well-known/agent-skills/index.json

## Endpoints

- GET https://trust.kit-rx.com/v1/x402/receipt ($0.002) params: echo?. Decodes the x402 v2 PAYMENT-SIGNATURE header sent with the request into a readable receipt: x402 version, scheme, CAIP-2 network and chain name, resource URL, the copied payment requirements, payer, recipient, value in atomic units and USD, USDC contract, nonce, validity window in ISO-8601 with seconds to expiry, signature length and prefix, extension keys, and pass/fail diagnostics. Computed locally, no upstream source.
- GET https://trust.kit-rx.com/v1/x402/preflight ($0.005) params: url. Sends an unpaid GET to an x402 endpoint and reports what it would charge before paying: HTTP status, redirects (max 3, re-validated), v2 PAYMENT-REQUIRED header or v1 body challenge and its validity, each accepts entry (scheme, CAIP-2 network/name, atomic amount, USD for canonical USDC, asset check, payTo, timeout, EIP-712 name/version), OFAC SDN payTo screen, resource, Bazaar extension, risk flags, host context from registry RDAP (registrar, domain age) and Cloudflare DoH.
- GET https://trust.kit-rx.com/v1/x402/find ($0.01) params: q, max_price?, network?, limit?. Search and discovery of paid x402 API endpoints for a plain-language need, across Ultravioleta DAO x402 Bazaar and 402 Index directories. Dedupes by resource URL; ranks by relevance, verification, uptime, price and recency. Each result: resource URL, short description, USDC price, CAIP-2 networks, sources, verification. The top 3 GET endpoints get a live unpaid check: valid x402 402, live price, networks, canonical USDC, risk flags, OFAC SDN payTo screen, RDAP domain age.
- GET https://trust.kit-rx.com/v1/compliance/sanctions ($0.01) params: address?, name?, threshold?. OFAC sanctions (AML/KYC) screening of a crypto wallet or a person, company, vessel or aircraft name against a dated snapshot of the U.S. Treasury SDN and non-SDN Consolidated lists. Address mode: exact match on OFAC-listed digital currency addresses (BTC, ETH/EVM, USDT, TRX, XMR, LTC, more). Name mode: fuzzy match on names and strong aliases ignoring case, accents, punctuation and word order, scored 0-100. Returns match flag, OFAC uid, type, programs, country, list date.

## Data sources

US FDA (openFDA), NLM RxNav/RxNorm, CMS NADAC (data.medicaid.gov), Wikidata, GLEIF, SEC EDGAR, US Census Geocoder, USGS EPQS, NOAA NWS, RDAP registries, Cloudflare DNS-over-HTTPS, and the checked websites themselves. Reports are informational summaries; verify critical decisions against the primary source.