402 Index primary sources — 2026-05-03

Project status in this pass

• No canonical standalone 402 Index whitepaper or litepaper surfaced.
• The clearest current source of truth is the live product site plus the first-party API and provider-verification docs.
• The materials consistently frame 402 Index as a protocol-agnostic discovery, monitoring, and verification layer for paid APIs rather than as a static list.

Primary-source snapshots

1) Live site / current positioning

• URL: https://402index.io/
• Key excerpt:
  • The homepage presents ecosystem-wide counts for indexed endpoints, payment-verified endpoints, providers, and health status across L402, x402, and MPP.
  • It also shows an “Agent Discovery” surface and a step-by-step payment flow, making clear that the product is built around machine discovery and paid-request execution rather than around human browsing alone.

2) About page / methodology

• URL: https://402index.io/about
• Key excerpt:
  • The about page says 402 Index is a protocol-agnostic directory of paid APIs designed for AI agents and explicitly names L402, x402, and MPP as supported protocols.
  • It explains that services are aggregated from sources such as x402 Bazaar, Satring, L402 Apps, Sponge, Tempo/MPP, self-registration, and .well-known discovery.
  • It also describes hourly health checks and protocol-specific verification logic, including Lightning header parsing, x402 payment-requirements validation, and MPP challenge validation.

3) API docs / programmable control plane

• URL: https://402index.io/api-docs
• Key excerpt:
  • The API docs expose a REST surface for service search, detail views, categories, health, registration, CSV export, opportunity analysis, and webhooks.
  • They define verification tiers such as domain-verified and payment-verified, describe hybrid semantic-plus-LIKE search, and document self-registration with protocol probing and review.
  • The docs also note that CSV export is L402-gated and that the service lists itself in its own directory, which is a strong dogfooding signal.

4) Provider verification / domain claim workflow

• URL: https://402index.io/verify
• Key excerpt:
  • The verification workflow lets a provider claim a domain, receive a token plus a verification hash, publish the hash at /.well-known/402index-verify.txt, and then edit or delete listings tied to that hostname.
  • This is strong evidence that 402 Index is packaging provider-side control-plane operations, not just public browsing.

5) MCP server source pointer

• URL: https://github.com/ryanthegentry/402index-mcp-server
• Key excerpt:
  • The archived MCP-server repository says the source has been consolidated into the 402index monorepo and positions the MCP server as an official way to query the directory from AI assistants.
  • Even though the repository is archived, it confirms the project’s agent-facing integration posture.

Working conclusion

402 Index is best cataloged as paid-API discovery and verification infrastructure for autonomous clients. The decisive evidence in this pass was the recurring combination of protocol-agnostic indexing, independent hourly payment verification, domain-claim and self-registration workflows, agent-facing API/MCP access, and health-aware ranking tiers. The key distinction is that 402 Index is operating a live trust-and-discovery layer for machine spending decisions instead of merely curating paid endpoint links.