402index

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).

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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

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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.

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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/.

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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

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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.

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