402 Index

Protocol-agnostic directory of paid APIs for AI agents.

What it is: a registry of HTTP 402–priced APIs across every major machine-payment protocol — L402 (Lightning), x402 (stablecoins), and MPP (Stripe/Tempo) — surfaced to AI agents via HTTP, RSS, Nostr, and MCP.

Who it's for: AI-agent developers looking for services to call, and API providers looking to get discovered by agents. The directory is community-owned: open source, MIT-licensed, no captive protocol.

Where it lives: 402index.io (production) · @402index (digest) · GitHub Issues (roadmap).

Quickstart

For agents (MCP)

One command adds 402 Index discovery + payment to any MCP host (Claude Desktop, Cursor, Cline, Windsurf):

npm install -g @402index/mcp-server

Then register it with your MCP host — see mcp-server/README.md for per-client instructions.

For agents (HTTP)

# Semantic search
curl "https://402index.io/api/v1/services?q=weather&verified=true&limit=10"

# Filter by protocol
curl "https://402index.io/api/v1/services?protocol=L402&health=healthy"

Full API reference at 402index.io/api-docs.

For API providers

Register your endpoint so agents can find it:

• Self-serve: POST https://402index.io/api/v1/register with your endpoint URL. The probe validates the 402 challenge, detects L402 and/or x402 support, and lists automatically.
• Pull request: add a YAML file under listings/ — see CONTRIBUTING.md.
• Already on Bazaar, Satring, or l402apps? You're already indexed — no action needed.

For contributors

git clone https://github.com/ryanthegentry/402index.git
cd 402index
npm install
npm test                # Run tests (node:test)
npm run dev             # Start dev server (nodemon)
npm run poll            # Pull from Bazaar + Satring manually
npm run healthcheck     # Run health checks manually

What's in the registry

Tens of thousands of endpoints across hundreds of verified providers, aggregated from the x402 Bazaar, Satring, l402apps.com, MPP's OpenAPI directory, and direct self-submissions — no gatekeeping by protocol.

Live numbers at 402index.io/api/v1/health.

Architecture

• Node.js + Express, SQLite via better-sqlite3, static HTML via template literals (no framework).
• Aggregators (src/aggregators/) poll Bazaar / Satring / l402apps on a schedule and upsert normalized listings.
• Health checker (src/health/checker.js) probes listings on a configurable interval, defaulting to 60 minutes (HEALTH_CHECK_INTERVAL_MS), with SSRF-safe fetch, records status, emits events.
• Semantic search via sqlite-vec + hybrid LIKE/vector re-rank, with circuit-breaker fallback to LIKE-only when the embeddings service is down.
• Distribution: HTTP API, MCP server, RSS, Nostr (NIP-99), webhooks (HMAC-SHA256).
• Verifier handles BOLT11 invoices (L402) and ERC-20 stablecoin challenges (x402), including x402-over-Lightning.

Deeper notes in CLAUDE.md and docs/.

Project layout

402index/
├── src/               # Application code (routes, aggregators, services, views)
├── mcp-server/        # @402index/mcp-server (published to npm)
├── listings/          # YAML listings for manually curated / exclusive providers
├── test/              # Tests (node:test)
├── scripts/           # Ops scripts (poll, healthcheck, backfills)
├── docs/              # Specs, API docs, protocol notes
└── .github/workflows/ # CI

Contributing

PRs welcome for listings, code, and docs. See CONTRIBUTING.md for the fork-branch-PR flow and CLAUDE.md for code style and the bug-fix protocol (failing-test-first).

Roadmap is the open issues list. Good starter tasks have the good-first-issue label.

Security

Please do not open a public issue for suspected vulnerabilities. See SECURITY.md for responsible-disclosure contacts and the threat model summary.

License

MIT. Use it, fork it, ship it.

Built by @ryanthegentry and the community. Questions → hello@402index.io or GitHub Discussions.