goodsong.dev x402 offerings

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-looking citation number paired with an invented case name. Checked against CourtListener. Does not check whether a case is still good law -- no free authoritative source publishes that.

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 data included) with OpenAlex as a fallback when no DOI is given.

Verify an FDA drug record: given a claim_type (approval, ndc, or recall) and its identifier, does that record actually exist, and does the given name match the canonical record? Checked against openFDA. Catches a fabricated or misattributed drug approval, NDC listing, or recall citation. Existence/status only, not medical advice.

Verify an SEC filing: given a filer's CIK and a claimed accession number, does that filing actually exist, and does its form type/filing date match what's claimed? Checked against SEC EDGAR's submissions API. Catches a fabricated or misattributed filing citation, including a real-looking accession number paired with an invented form type or date.

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 the page. Checked via direct fetch and the Internet Archive.

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.dev advisories.

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 abandoned. Checked against the GitHub REST API.

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.