Cowrie Research

402-index

3 min read

402 Index

  • Name: 402 Index
  • URL: https://402index.io/
  • Category: paid-API directory / payment-verification control plane
  • Tags: bitcoin-ecosystem ethereum-ecosystem
  • Summary: 402 Index is one of the better machine-payment discovery notes because it does more than list endpoints. It health-checks paid APIs, validates payment challenges, supports provider claims via .well-known, and exposes agent-facing search and API surfaces across L402, x402, and MPP. The directory itself is not the story; the verification layer is.
  • 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/header checks, x402 payment-requirements validation, and MPP challenge parsing
  • Key claims:
    • The about page says 402 Index is a protocol-agnostic directory of paid APIs for AI agents covering L402, x402, and MPP, which is stronger than the framing of a niche Lightning list or x402 showcase
    • The site and docs both emphasize independent hourly verification, making the product materially different from static ecosystem catalogs that do not continuously test payment readiness
    • The API docs expose verification tiers such as domain-verified and payment-verified, which suggests the service is trying to operate a machine-trust ranking layer rather than only expose search results
    • The docs show 402 Index supports self-registration, automatic protocol detection, .well-known discovery, and provider domain claims, which materially broadens it into an indexing and control-plane system for providers as well as buyers
    • The CSV export being L402-gated and the docs explicitly saying the service is listed in its own directory show the product is also dogfooding paid-API mechanics rather than only documenting them
    • The about page’s methodology section explains protocol-specific verification logic for L402, x402, and MPP, which is a strong sign that 402 Index is packaging operational payment intelligence for agents, not just endpoint metadata
  • 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.
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