# Services from goodsong.dev on Zero

> goodsong.dev serves 8 paid API services for AI agents, indexed by Zero. Each is callable per call with payment handled by Zero.

Canonical page: https://www.zero.xyz/host/goodsong.dev
Live health (JSON, refreshed every minute): https://www.zero.xyz/host/goodsong.dev/health.json

## Services

- [RealCite Case Citation Verifier](https://www.zero.xyz/c/realcite-case-citation-verifier-70e3d981/llms.txt): $0.01/call via x402. Verifies whether a legal case citation exists in CourtListener and whether the provided case name matches the canonical record, catching fabricated citations.
- [verify-citation](https://www.zero.xyz/c/verify-citation-14d843f0/llms.txt): $0.005/call via x402. Verifies whether a citation exists, checks if it has been retracted, and confirms that title/authors/year/journal metadata match the canonical academic record via Crossref and OpenAlex.
- [RealCite Drug — FDA Drug Record Verifier](https://www.zero.xyz/c/realcite-drug-fda-drug-record-verifier-4f08af8b/llms.txt): $0.005/call via x402. Verifies whether an FDA drug record (approval, NDC listing, or recall) actually exists and whether a given name matches the canonical record, checked against openFDA.
- [RealCite Filing Verifier](https://www.zero.xyz/c/realcite-filing-verifier-55ebdce5/llms.txt): $0.005/call via x402. Verifies an SEC filing by checking whether a given CIK and accession number exist in EDGAR, and whether the claimed form type and filing date match the official record.
- [RealCite URL Verifier](https://www.zero.xyz/c/realcite-url-verifier-3dab78a0/llms.txt): $0.005/call via x402. Verifies a URL by checking if it resolves, its final HTTP status and redirect chain, whether it is archived on the Wayback Machine, and optionally whether expected text appears on the live page.
- [verify-package](https://www.zero.xyz/c/verify-package-2a8f5276/llms.txt): $0.005/call via x402. Checks whether an npm, PyPI, or crates.io package exists, is deprecated/yanked, and has known security vulnerabilities via OSV.dev advisories.
- [realdep-repo](https://www.zero.xyz/c/realdep-repo-ddc43cda/llms.txt): $0.005/call via x402. Verifies that a GitHub repository exists and checks whether it is archived or disabled, catching stale or broken repo dependencies.
- [realx402-seller](https://www.zero.xyz/c/realx402-seller-754e839e/llms.txt): $0.005/call via x402. Verifies an x402 seller endpoint by checking it responds with a valid 402 challenge, validates its schema consistency, and screens its payout address against sanctions oracles

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

- [Zero catalog index](https://www.zero.xyz/llms.txt)