# Fee Now — Bitcoin fee calculator + L402 forecast for AI agents

> Live Bitcoin mempool fee rates (sat/vB + USD). Free JSON for current fees. Paid Lightning L402 endpoint for a best-time-to-send forecast. Operator: Hexbox Tools. No KYC. Payments to hexbox@hexbox-ln.hexboxtools.workers.dev.

## Free (no payment)

- GET https://hexbox-fees.hexboxtools.workers.dev/api/fees — current recommended fees, USD price, costs for common tx sizes, send-or-wait advice
- GET https://hexbox-fees.hexboxtools.workers.dev/api/agent.json — machine discovery document (endpoints, price, auth)
- GET https://hexbox-fees.hexboxtools.workers.dev/health — liveness
- GET https://hexbox-fees.hexboxtools.workers.dev/should-i-send-bitcoin-now — human+agent SEO page with live call
- GET https://hexbox-fees.hexboxtools.workers.dev/bitcoin-fee-history — 24h median fee history summary
- GET https://hexbox-fees.hexboxtools.workers.dev/fees/next-block | /fees/half-hour | /fees/hour | /fees/economy — per-target pages
- GET https://hexbox-fees.hexboxtools.workers.dev/fees/target/{satvb} — "when fees near N sat/vB" page

## Paid (L402 Lightning, 21 sats)

- GET https://hexbox-fees.hexboxtools.workers.dev/api/v1/forecast — best-time-to-send recommendation, 24h context, mempool depth, savings example
- GET https://hexbox-fees.hexboxtools.workers.dev/api/v1/forecast/sample — free schema example (not live; no payment)

### How to pay (agents)

1. GET https://hexbox-fees.hexboxtools.workers.dev/api/v1/forecast → HTTP 402
2. Read WWW-Authenticate: L402 macaroon="...", invoice="lnbc..."
3. Pay the bolt11 invoice with any Lightning wallet / node / agent payer
4. Retry the same URL with header: Authorization: L402 <macaroon>:<preimage>
5. Receive JSON forecast. Token valid ~1 hour; same preimage may be reused within TTL.

OpenAPI: https://hexbox-fees.hexboxtools.workers.dev/openapi.json
AI plugin: https://hexbox-fees.hexboxtools.workers.dev/.well-known/ai-plugin.json
Docs: https://hexbox-fees.hexboxtools.workers.dev/agents
Tips / support: lightning:hexbox@hexbox-ln.hexboxtools.workers.dev

## Why agents pay

If your agent broadcasts on-chain BTC, a bad fee window wastes more than 21 sats on a single typical send. This forecast packs mempool + 24h history into one decision object so tools can choose send_now vs wait vs economy without scraping HTML.