# Flying Money

> Prepaid, capped budgets for AI agents and people ("hand over a budget, not your wallet"). A funder locks USDC for ONE payee, spendable by ONE spender key until expiry. The spender pays with EIP-712 "notes" signed over a cumulative total; the payee verifies locally and redeems the latest note on-chain in one transaction. Same contract source on every supported EVM chain. No token.

Deployed now: Arbitrum Sepolia (421614, testnet). Unaudited. No mainnet deployment yet; mainnets will launch under immutable caps.

**AI agent asked to set up payments? Read [https://useflyingmoney.vercel.app/agent.md](https://useflyingmoney.vercel.app/agent.md) and follow it.**

Key rules for agents:
- You can only pay the payee named on your certificate, never more than its face value.
- On HTTP 402 with a `Flying-Money-Offer` header, sign a Note with cumulative = max(accepted, consumed + price) and memo = a fresh requestId, save it, and retry with `Flying-Money-Note`. On a timeout, resend the SAME note. Never sign a higher one because of a network failure.
- Never sign a cumulative above face value. Never ask the user for their main wallet key.

## Docs
- [Setup for AI agents](https://useflyingmoney.vercel.app/agent.md): add the MCP server, tell your owner your address, ask for budgets
- [Quickstart for developers](https://useflyingmoney.vercel.app/docs/agents.md): pay a Flying Money API in a few lines
- [Protocol](https://useflyingmoney.vercel.app/docs/protocol.md): EIP-712 types, headers, seller and buyer algorithms
- [Contract](https://useflyingmoney.vercel.app/docs/contract.md): functions, events, errors, caps, invariants
- [MCP server](https://useflyingmoney.vercel.app/docs/mcp.md): tools fm_status, fm_explain, fm_quote, fm_paid_fetch, fm_request_budget, fm_request_status
- [Client SDK](https://useflyingmoney.vercel.app/docs/client.md): the buyer side and its durable outbox
- [Sellers](https://useflyingmoney.vercel.app/docs/server.md): accept notes with middleware; the redeemer
- [People & shops](https://useflyingmoney.vercel.app/docs/shops.md): the QR counter flow
- [Live demo](https://useflyingmoney.vercel.app/demo): an agent paying a Flying Money API, with real testnet transactions
- [Everything in one file](https://useflyingmoney.vercel.app/llms-full.txt)

## Reference
- [Deployments (JSON)](https://useflyingmoney.vercel.app/.well-known/flying-money.json)
- [Deployments (page)](https://useflyingmoney.vercel.app/chains)
- [Guarantees & threat model](https://useflyingmoney.vercel.app/docs/guarantees.md)

## Optional
- [Story: flying money, 804 CE](https://useflyingmoney.vercel.app/docs/story.md)
- [FAQ](https://useflyingmoney.vercel.app/docs/faq.md)
- [Source](https://github.com/raldblox/flying-money)