Agent to Agent payments (a402)
What is a402?
a402 is the open payment protocol behind Beep Pay. a402 stands for agent 402: payment required
It extends the original HTTP 402: Payment Required status code into a verifiable, on-chain payment layer that lets agents pay and unlock digital resources autonomously — no human checkout, no custodians, no intermediaries.
At its core, a402 defines how clients (agents), facilitators, and merchants interact to perform atomic, yield-aware USDC transfers tied to digital actions like API calls, model inference, file delivery, or app access.
The result: instant, trustless machine-to-machine payments — stable, programmable, and cryptographically verifiable.
💡 The Idea
HTTP 402 has existed for decades as a reserved response code for “Payment Required,” but until now it had no implementation. a402 revives that concept by turning HTTP requests into programmable payment flows using stablecoins like USDC.
That means any GET, POST, or RUN request can include a verified, on-chain payment — allowing agents and apps to pay as part of the same network call.
⚙️ How It Works
Client (Agent) requests access to a protected resource (e.g., API, AI endpoint, dataset).
Server (Merchant) responds with:
HTTP 402 Payment Required Payment-Request: <encoded a402 payload>Client executes the stablecoin transfer and sends back a payment receipt.
Server or Facilitator verifies the receipt on-chain.
Once verified, access is granted instantly.
Every transaction is stateless, verifiable, and non-custodial — native to the web stack.
💸 Why It Matters
a402 makes payments a first-class citizen of the web. Instead of bolting on legacy payment SDKs or redirect flows, it embeds money movement directly into HTTP.
This enables:
Pay-per-call APIs (monetize inference, data, compute)
Pay-per-second streaming for media or model usage
Agent-to-agent commerce for autonomous systems
Instant microtransactions with no intermediaries or credit rails
In short, a402 bridges the internet and the financial layer — seamlessly, natively, and globally.
🔐 Key Properties
Stablecoin-native: built around on-chain USDC transfers
Instant settlement: sub-second confirmation (Sui)
Verifiable receipts: every payment has a cryptographic proof
Non-custodial: sender and receiver control their own vaults
Composable: works with existing web standards (HTTP headers, status codes)
How does a402 compare to x402 or L402?
L402 (Lightning): macaroon‑based auth + satoshi payments; great for BTC, requires Lightning infra.
x402 (Coinbase): strong push for EVM chains, lacks identity.
a402: built‑in identity/authorization, off‑chain session channels for bursty micro‑flows.
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