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cramberries099-bit
cramberries099-bit

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I launched two L402 APIs for AI agents — clean data for 10 sats, mempool forensics for 2,500

#bitcoin #lightning #ai #api

AI agents can write code, browse the web and run tools — but the moment they need to pay for an API, the flow collapses into human infrastructure: signups, API keys, credit cards, monthly plans.

L402 fixes that. The payment is the credential. So I built two production-light APIs that any agent (or human) can consume autonomously over Bitcoin Lightning, and put them live:

🔗 https://l402-ai-gateway.onrender.com

What's for sale

Endpoint Price What it does
POST /v1/data/clean-scrape 10 sats Takes raw web content and returns clean, structured JSON an LLM can consume directly
POST /v1/forensic/mempool-arbitrage-audit 2,500 sats Analyzes a real Bitcoin transaction (fee rate, RBF signaling, inputs/outputs, confirmations) using live mempool.space data, and compares live BTC prices across Kraken, Coinbase and Bitstamp to flag arbitrage spreads

No accounts. No keys. You call, you get a 402, you pay the Lightning invoice, you retry with the proof, you get the data.

How the paywall works

The middleware is protocol-standard, not a custom hack:

  1. Request without payment → 402 Payment Required with a WWW-Authenticate: L402 macaroon="…", invoice="lnbc…" header (plus the same data as JSON).
  2. The macaroon is HMAC-chained and attenuated by endpoint, payment hash, amount and expiry — a token bought for the 10-sat endpoint is rejected on the 2,500-sat one.
  3. Pay the invoice (issued by a real LNbits wallet) → you get the preimage.
  4. Retry with Authorization: L402 <macaroon>:<preimage> → the server verifies sha256(preimage) == payment_hash locally and serves the result.

It works out of the box with standard tooling like Lightning Labs' lnget — point it at an endpoint and the pay-and-retry cycle is automatic.

Discovery is built in too: a machine-readable manifest at /.well-known/l402.json, public pricing at /pricing, interactive OpenAPI docs at /docs, and the service announces itself on Nostr with NIP-89 handler events (kind 31990) so agents can find it without me doing marketing.

Under the hood: FastAPI, an in-memory TTL cache (repeat calls are cheap), and live upstream data — nothing in the forensic report is mocked.

Honest limitations

This is a launch, not a victory lap:

  • It runs on a free hosting tier that sleeps when idle — the first call can take a few seconds to wake up.
  • The receiving wallet is a custodial LNbits demo instance. Fine for the first sats, not where I'd keep real revenue.
  • It currently has zero paying customers. That's why this post exists.

Try it / break it

The cheapest call costs 10 sats — less than a cent. If you're building agents, trading bots or L402 tooling, I'd genuinely love for you to:

  1. Hit the endpoint and run the full pay flow.
  2. Tell me what the output is missing for your use case.
  3. If it fits, I'm helping the first 10 builders integrate it for free (the calls themselves stay at list price — a real 10-sat payment is the feedback signal I care about).

Docs and manifest are public, the code structure is a standard FastAPI service, and the paywall answers with a real invoice from a real wallet. The machine economy needs services that are actually buyable by machines — this is my first one.

What should the third endpoint be?

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