Verify an x402 seller before paying it: does it exist and respond with a well-formed 402 challenge, is its own declared input/output schema internally consistent, and is its payout address sanctioned? Checked live against the seller itself plus Chainalysis's sanctions oracle and Blockscout (Base payTo addresses only). Confirms the checkable things about a seller check out -- not a guarantee of trustworthiness, which no free source can promise.
# 1. Ask the endpoint what it costs (no payment, no wallet needed): curl -i -X POST 'https://goodsong.dev/verify/seller' # -> HTTP/1.1 402 Payment Required # the response carries the price, asset and pay-to address. # 2. Pay and retry with any x402 client: npx x402-fetch -X POST 'https://goodsong.dev/verify/seller'
Endpoint: https://goodsong.dev/verify/seller. Operated by goodsong.dev, not by Animica. Price and availability were correct at the last probe on 2026-09-02 and are set by the operator, who may change them.
Verify a legal case citation: does it exist, and does the given case name match the canonical record? Catches a fabricated case citation, including a real-looki…
Verify a citation: does it exist, is it retracted, and do the given title/authors/year/journal match the canonical record? Checked against Crossref (retraction …
Verify a package: does it exist, is it deprecated or yanked, and does it have known vulnerabilities? Checked against the npm/PyPI/crates.io registry plus OSV.de…
Verify a GitHub repo: does it exist, is it archived or disabled? Catches an agent recommending or depending on a repo that's been renamed, taken down, or abando…
Verify a URL: does it resolve, what's the final status and redirect chain, is it archived on the Wayback Machine, and (optionally) does expected text appear on …