Multi-Token Agent

An agent that handles payments in multiple tokens — ETH, WVRN, and USDC — with proper approval management.

Full Code


import { ethers } from 'ethers'
import { WeavrnClient } from '@weavrn/sdk'
 
const PRIVATE_KEY = process.env.PRIVATE_KEY!
 
// Token addresses on Base Sepolia
const TOKENS = {
  WVRN: '0x1c17b46bd9b37024e86EA5fe05e1dE835aE1Ce0E',
  USDC: '0x...', // your USDC address
}
 
async function main() {
  const provider = new ethers.JsonRpcProvider('https://sepolia.base.org')
  const signer = new ethers.Wallet(PRIVATE_KEY, provider)
  const client = new WeavrnClient({ signer, chainId: 84532 })
 
  if (!(await client.isRegistered())) {
    await client.register('MultiTokenAgent', 'https://example.com/agent.json')
  }
 
  // Approve all tokens upfront with large allowances
  await approveTokens(client)
 
  // Now pay in any token
  const recipient = '0xRecipient...'
 
  // ETH — no approval needed
  await client.pay(recipient, ethers.parseEther('0.001'), {
    memo: 'eth payment',
  })
 
  // WVRN (18 decimals)
  await client.payERC20(recipient, TOKENS.WVRN, ethers.parseEther('100'), {
    memo: 'wvrn payment',
    decimals: 18,
  })
 
  // USDC (6 decimals)
  await client.payERC20(recipient, TOKENS.USDC, ethers.parseUnits('25', 6), {
    memo: 'usdc payment',
    decimals: 6,
  })
}
 
async function approveTokens(client: WeavrnClient) {
  const MAX_ALLOWANCE = ethers.MaxUint256
 
  // Approve router for payments
  for (const [name, address] of Object.entries(TOKENS)) {
    console.log(`Approving ${name} for PaymentRouter...`)
    await client.approveRouter(address, MAX_ALLOWANCE)
  }
 
  // Approve escrow for escrow-based payments
  for (const [name, address] of Object.entries(TOKENS)) {
    console.log(`Approving ${name} for EscrowRouter...`)
    await client.approveEscrow(address, MAX_ALLOWANCE)
  }
 
  // Wait for approvals to propagate
  await new Promise(r => setTimeout(r, 3000))
}
 
main().catch(console.error)

Token Decimals

Different tokens use different decimal places. Always match the decimals parameter to the token:

Token	Decimals	1 unit in smallest unit
ETH	18	`ethers.parseEther('1')`
WVRN	18	`ethers.parseEther('1')`
USDC	6	`ethers.parseUnits('1', 6)`

The decimals option in payERC20 only affects how the returned amount and fee strings are formatted — the on-chain transfer uses the raw bigint amount you provide.

Approval Strategy

Two approaches:

Max Approval (Simpler)

Approve ethers.MaxUint256 once per token per contract. Fewer transactions, but grants unlimited spending.


await client.approveRouter(token, ethers.MaxUint256)

Exact Approval (Safer)

Approve the exact amount needed before each transaction. More gas, but limits exposure.


await client.approveRouter(token, ethers.parseEther('100'))
await client.payERC20(recipient, token, ethers.parseEther('100'))

Important

approveRouter and approveEscrow are separate approvals to different contracts
If you use both payment and escrow features with the same token, approve both
Wait 2-3 seconds after approval before the next transaction