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Why DNS discovery

Agents with internet access can resolve DNS before making any HTTP request. If you publish your L402 endpoint as a DNS TXT record, agents discover it automatically — even before hitting your API.

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TXT record format

l402._payment.yourdomain.com  TXT  "v=l402 endpoint=https://api.yourdomain.com/data price=10sat docs=https://yourdomain.com/docs"
Fields:
  • v=l402 — protocol identifier
  • endpoint= — your L402-protected URL
  • price= — price in sats (optional, informational)
  • docs= — link to your docs (optional)

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Setup on Cloudflare

  1. Go to Cloudflare Dashboard → DNS
  2. Add a new record:
TypeNameContentTTL
TXTl402._paymentv=l402 endpoint=https://api.yourdomain.com/data price=10sat docs=https://yourdomain.com/docsAuto

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Verify with dig

dig TXT l402._payment.yourdomain.com

# Expected output:
# l402._payment.yourdomain.com. 300 IN TXT "v=l402 endpoint=https://api.yourdomain.com/data price=10sat docs=..."

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How agents use it

import { discoverL402Endpoint } from "l402-kit/agent";

// Agent resolves DNS to find your endpoint
const endpoint = await discoverL402Endpoint("yourdomain.com");
// Returns: "https://api.yourdomain.com/data"

const result = await client.fetch(endpoint);

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l402-kit’s own record

The example below uses a fictional domain (api.example.com) to illustrate the format — replace it with your real endpoint. 
dig TXT l402._payment.l402kit.com
# v=l402 endpoint=https://api.example.com/api/demo price=1sat docs=https://docs.l402kit.com

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Benefits

  • Zero HTTP overhead — discovery before any API call
  • Agent-native — DNS is how machines find services, not humans
  • No API key needed — completely open discovery
  • Cacheable — TTL controls how often agents re-resolve
See .well-known/agent.json for the complementary HTTP discovery standard.