Read ERC20 balances and EVM chain data

Query token balances, allowances, and basic onchain state for any EVM address on Base and Ethereum mainnet. No node required.

$0.002 USDC / call free trial: 10/day per IP contabo

Endpoint

POST https://contabo-vps.taild7e69a.ts.net/chain/api/chain

Data source: Base + Ethereum RPC

Parameters

Param	Type	Description
`address`	string (body JSON)	Wallet or contract address 0x...
`token`	string (body JSON, optional)	ERC20 contract address; omit for native balance

Example request

curl -X POST "https://contabo-vps.taild7e69a.ts.net/chain/api/chain" \
  -H "Content-Type: application/json" \
  -d '{ "address": "0x198f3895551B309fF5C5F59e690FB0823d10EA93", "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" }'

Example response

{
  "address": "0x198f...EA93",
  "token": "USDC",
  "balance": "0.068",
  "decimals": 6,
  "network": "eip155:8453"
}

How payment works (x402)

Call the endpoint without any payment header → you get 402 Payment Required with the exact price, the USDC contract, the network (eip155:8453 = Base), and the pay-to address.
Pay 0.002 USDC on Base to the pay-to address — with any wallet, the Coinbase CDP x402 SDK, or any x402 client library.
Retry the same request with the X-PAYMENT header set to the base64-encoded signed payment payload → 200 with JSON.

# 1. Get the 402 payment requirements
curl -s -X POST "https://contabo-vps.taild7e69a.ts.net/chain/api/chain" -H "Content-Type: application/json" -d '{ "address": "0x198f3895551B309fF5C5F59e690FB0823d10EA93", "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" }'

# 2. Pay 0.002 USDC on Base, then retry with the payment proof
curl -X POST "https://contabo-vps.taild7e69a.ts.net/chain/api/chain" \
  -H "Content-Type: application/json" \
  -H "X-PAYMENT: <base64-signed-payment-payload>" \
  -d '{ "address": "0x198f3895551B309fF5C5F59e690FB0823d10EA93", "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" }'

Facilitators: Coinbase CDP and PayAI (no API key needed for either). Scheme: x402 v2 exact. Asset: USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base.

Free trial

Every IP gets 10/day free calls to this endpoint — no payment needed. Free calls run automatically when you call without an X-PAYMENT header. The X-Free-Remaining response header shows how many free calls you have left today. When the quota is exhausted, the request falls through to the normal 402 payment flow.

FAQ

Which networks are supported?
Base (eip155:8453) and Ethereum mainnet (eip155:1).

Can I batch multiple addresses?
One address per call. Batch by making parallel calls.

Is this real-time?
Reads the latest finalized block, typically <15s behind head.

Do I need an API key?
No. This API uses x402: call the endpoint, receive a 402 Payment Required with the price, pay in USDC on Base, and retry with the X-PAYMENT header. No signup, no API key, no account.

Which facilitators are supported?
Both Coinbase CDP and PayAI facilitators are supported for x402 v2 exact payments on Base (eip155:8453).

What if my payment is too low?
The facilitator verifies the on-chain amount against the price. If underpaid, you get 402 again; pay the full amount and retry.

All 37 x402 API docs · Postman collection (download) · About this API