t402

name	t402
version	2.8.0
description	HTTP-native stablecoin payment protocol for AI agents
author	t402-io
license	Apache-2.0
capabilities	["pay","verify","bridge","swap","sign","observe"]
tags	["payment","stablecoin","blockchain","http-402","ai-agent","mcp"]

t402 Payment Skill

Teach your AI agent to pay for web resources using USDT/USDC stablecoins across 25+ blockchain networks.

What You Can Do

• Pay for HTTP resources — automatically handle 402 Payment Required responses
• Check balances — query wallet balances across all supported networks
• Bridge tokens — move USDT0 between chains via LayerZero
• Swap tokens — exchange tokens via DEX aggregators
• Verify agents — check ERC-8004 on-chain identity and reputation
• Monitor payments — track payment flows and metrics

How HTTP 402 Payment Works

1. Request a resource:     GET https://api.example.com/data
2. Receive 402 response:   { amount: "1000000", asset: "USDC", network: "eip155:8453" }
3. Sign payment:           EIP-3009 TransferWithAuthorization (gasless)
4. Retry with payment:     GET /data + PAYMENT-SIGNATURE header
5. Receive resource:       200 OK + data

The entire flow happens in a single request-response cycle. No accounts, API keys, or checkout flows needed.

Available MCP Tools

Core Payment (always available)

Tool	Description
t402/getBalance	Get token balances on a specific network
t402/getAllBalances	Get balances across all networks
t402/pay	Execute a stablecoin payment
t402/payGasless	Pay without gas (ERC-4337)
t402/getTokenPrice	Get current token prices
t402/getGasPrice	Get gas prices per network
t402/estimatePaymentFee	Estimate payment cost
t402/compareNetworkFees	Find cheapest network
t402/getBridgeFee	Quote a cross-chain bridge
t402/bridge	Execute cross-chain transfer
t402/quoteBridge	Get reusable bridge quote
t402/executeBridgeQuote	Execute from quote

WDK Wallet (requires seed phrase)

Tool	Description
wdk/getWallet	Get wallet info
wdk/getBalances	Multi-chain balances
wdk/transfer	Send stablecoins
wdk/swap	Swap tokens (Velora)
wdk/quoteSwap	Get swap quote
wdk/executeSwap	Execute from quote
t402/autoPay	Smart auto-payment — fetch URL, handle 402, pay, return content

Agent Identity (ERC-8004)

Tool	Description
erc8004/resolveAgent	Look up agent identity
erc8004/checkReputation	Query reputation score
erc8004/verifyWallet	Verify payment address

Unified (advanced)

Tool	Description
t402/smartPay	Intelligent payment routing
t402/paymentPlan	Multi-step payment planning

Supported Networks

EVM (25 mainnet chains)

Ethereum, Base, Arbitrum, Optimism, Polygon, Avalanche, BNB, Berachain, Celo, Ink, Unichain, MegaETH, Flare, Kaia, Mantle, Sei, Conflux, Monad, Rootstock, XLayer, Fantom, HyperEVM, Plasma, Stable, Corn

Non-EVM

Solana, TON, TRON, NEAR, Aptos, Tezos, Polkadot, Stacks, Cosmos, Bitcoin, Lightning, Stellar, Spark

Supported Tokens

• USDT0 — Tether omnichain (EIP-3009, gasless)
• USDC — USD Coin (EIP-3009)
• USDT — Legacy Tether (approve+transferFrom)
• USAT — Tether America USD

Security Rules

1. Always confirm before payment — never auto-execute without user approval
2. Never expose seed phrases — use environment variables
3. Verify recipients — use erc8004/verifyWallet before paying unknown agents
4. Set spending limits — use the policy engine for budget enforcement
5. Check prices first — use t402/estimatePaymentFee before committing

Quick Start

As an AI Agent (MCP)

npm install @t402/mcp

Configure in your MCP client with a WDK seed phrase. The t402/autoPay tool handles the entire 402 flow automatically.

Programmatic (TypeScript)

import { createT402Client, wrapFetchWithPayment } from "@t402/core";

const client = createT402Client({ signer: myWallet });
const fetch402 = wrapFetchWithPayment(fetch, client);

// Just fetch — payment happens automatically on 402
const data = await fetch402("https://paid-api.example.com/data");

Learn More

• Documentation
• GitHub
• Demo
• Protocol Spec