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Overview

ACN uses USDC on Base for all payments. The payment model is simple:
  1. Deposit USDC into your ACN balance
  2. Pay per call — each API execution atomically deducts from your balance
  3. Automatic refunds — failed calls (5xx errors, timeouts) are refunded instantly
No subscriptions. No monthly invoices. No credit cards. Just per-call micropayments that agents can execute autonomously.

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The X402 Protocol

ACN implements the X402 protocol — an open standard for machine-to-machine payments. X402 enables agents to pay for services without human intervention by embedding payment authorization directly in HTTP requests.

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Payment Flow

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Deposit

Send USDC to the ACN platform wallet on Base. Once the transaction is confirmed on-chain, your balance is credited automatically. 
# Check your current balance
curl https://api.acn.exchange/v1/wallet/balance \
  -H "Authorization: Bearer acn_sk_your_key"

{
  "balance_usdc": "10.50",
  "total_deposited_usdc": "25.00",
  "total_spent_usdc": "14.50"
}

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Per-Call Billing

When you execute a call, the cost is deducted atomically before the request is proxied to the provider:
  • If you don’t have sufficient balance, the call is rejected with a clear error
  • If the provider returns a 5xx error or times out, the charge is automatically refunded
  • 4xx errors (bad request, unauthorized) are not refunded — these are caller errors

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Settlement

ACN settles with providers in daily batches (2 AM UTC):
  1. All calls for the period are aggregated per provider
  2. Platform fee is deducted
  3. Net amount is sent as a single USDC transfer on Base
  4. Settlement transaction hash is recorded

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Pricing Model

Providers set their own per-call pricing in USDC. Prices are displayed in discovery results so agents can make cost-aware decisions: 
{
  "pricing": {
    "model": "per_call",
    "price_per_call_usdc": "0.002"
  }
}
Typical call prices range from 0.001to0.001 to 0.05 USDC depending on the service complexity.

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Minimum Deposit

The minimum deposit is $5 USDC. This ensures the on-chain transaction fee is a negligible fraction of the deposit amount.

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Supported Currency & Network

PropertyValue
CurrencyUSDC
NetworkBase (Ethereum L2)
USDC Contract0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
Settlement FrequencyDaily (2 AM UTC)
Base is an Ethereum L2 with low transaction fees (typically under $0.01), making it ideal for micropayments.

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For Agents

Agents equipped with a wallet can handle payments entirely autonomously:
  1. Agent’s wallet holds USDC on Base
  2. Agent deposits into ACN balance as needed
  3. Agent executes calls — payments happen automatically
  4. No human approval needed per call
See Equip an Agent with a Wallet for setup instructions.