Cowrie Research

402-index

2 min read

402 Index

  • Name: 402 Index
  • URL: https://402index.io/
  • Category: paid-API directory / payment-verification layer
  • Tags: bitcoin-ecosystem ethereum-ecosystem
  • Summary: 402 Index is a paid-API directory with a verification sidecar. The directory itself is ordinary. The thing worth keeping is the operator layer that tests 402 challenges, scores listings, and decides what discovery data agents get.
  • What it does:
    • Aggregates paid API endpoints across L402 Lightning services, x402 crypto-micropayment services, and MPP/Tempo machine-payment services into one searchable directory
    • Continuously health-checks indexed endpoints and treats a valid 402 Payment Required challenge as the healthy state for paid APIs
    • Exposes a REST API with filtering, hybrid search, verification tiers, category trees, health stats, opportunities analysis, webhook subscriptions, RSS feeds, and CSV export
    • Supports agent-facing discovery through an MCP server and positions the directory explicitly as infrastructure for AI agents making autonomous API-buying decisions
    • Lets providers self-register endpoints, then verifies protocol compliance before review and publication
    • Lets providers claim existing listings by posting a verification hash at /.well-known/402index-verify.txt, after which they can edit pricing, descriptions, categories, and even soft-delete listings for their own domains
    • Tracks payment-verification quality differently by protocol, including Lightning token or header checks, x402 payment-requirements validation, and MPP challenge parsing
  • Key claims:
    • This is still a directory. The verification loop is why the note earns space.
    • The hourly checks matter because static listings do not tell agents whether a paid API is still returning a valid challenge.
    • Verification tiers plus the /.well-known claim flow make this an admission and trust layer for providers, not just a search page for buyers.
    • The service also dogfoods paid-request mechanics through gated exports and its own API surface, which keeps the note from collapsing into passive catalog software.
    • Keep the note on discovery and verification control, not on generic paid-API ecosystem mapping.
  • Whitepaper: No canonical standalone 402 Index whitepaper or litepaper surfaced in this pass. The clearest source of truth was the live product site, API docs, and provider-verification documentation; see ../whitepapers/402-index-primary-sources-2026-05-03.md.
  • Sources:

Internal linkages

Control surface

  • The leverage sits in listing admission, protocol-detection heuristics, challenge-validation rules, /.well-known domain claims, ranking or verification tiers, and crawler cadence.

  • Directory power, not rail power.

  • Last reviewed: 2026-06-16 UTC

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