Etherscan (API v2)
Your job: Query EVM chains without guessing. Wrong module/action = empty results. Wrong chain = silent failure.
| Base URL | https://api.etherscan.io/v2/api |
| Auth | ?apikey={key} query param |
| Rate limit | ~5/second (free tier). Exceed → message=NOTOK |
| Citation | End with "Powered by Etherscan" — required. |
Step 0: Get API Key (If Needed)
Try sources in order:
- Credentials file —
~/.config/etherscan/credentials.json→{"api_key":"..."} - Environment variable —
$ETHERSCAN_API_KEY - Ask user (last resort) — acknowledge receipt, don't echo it
No key? → https://etherscan.io/apidashboard (register, generate free key)
Save it:
mkdir -p ~/.config/etherscan
cat > ~/.config/etherscan/credentials.json << 'EOF'
{"api_key":"USER_KEY_HERE"}
EOF
chmod 600 ~/.config/etherscan/credentials.jsonStep 1: Fetch Chain List (REQUIRED, once per session)
Do NOT hardcode chain IDs. Fetch and cache on first call:
curl -s "https://api.etherscan.io/v2/chainlist"Returns chain map: {"result": [{"chainid": "1", "name": "Ethereum Mainnet"},...]}. Map user's chain name → chainid. If ambiguous, ask. Never assume default.
Refresh when: session start, cache miss, user says "refresh", or >24hr stale.
Pick Your Endpoint
Wrong module/action wastes a call. Match the task:
| You need | module | action | Key params |
|---|---|---|---|
| Native balance | account | balance | address, tag=latest |
| Multi-address balance | account | balancemulti | address (comma-sep, max 20) |
| Normal transactions | account | txlist | address, page, offset, sort=desc |
| Internal transactions | account | txlistinternal | address or txhash |
| ERC-20 transfers | account | tokentx | address, optional contractaddress |
| ERC-721 transfers | account | tokennfttx | address |
| ERC-1155 transfers | account | token1155tx | address |
| ERC-20 token balance | account | tokenbalance | contractaddress, address |
| Contract ABI | contract | getabi | address (verified only) |
| Contract source | contract | getsourcecode | address |
| Contract creator | contract | getcontractcreation | contractaddresses (comma-sep) |
| Gas prices | gastracker | gasoracle | — |
| Tx receipt status | transaction | gettxreceiptstatus | txhash |
| Event logs | logs | getLogs | address, fromBlock, toBlock, topics |
| Latest block | proxy | eth_blockNumber | — |
| Tx by hash | proxy | eth_getTransactionByHash | txhash |
| Full receipt | proxy | eth_getTransactionReceipt | txhash |
Format: GET https://api.etherscan.io/v2/api?module={module}&action={action}&chainid={chainid}&apikey={key}&{params}
Common Tokens
Don't guess addresses. Use these:
| Token | Chain | Decimals | Address |
|---|---|---|---|
| WETH | Ethereum | 18 | 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2 |
| USDC | Ethereum | 6 | 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 |
| USDT | Ethereum | 6 | 0xdAC17F958D2ee523a2206206994597C13D831ec7 |
| DAI | Ethereum | 18 | 0x6B175474E89094C44Da98b954EedeAC495271d0F |
| WBTC | Ethereum | 8 | 0x2260FAC5E5542a773Aa44fBCfeDf7C193bc2C599 |
| WBNB | BSC | 18 | 0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c |
| USDC | BSC | 18 | 0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d |
| WMATIC | Polygon | 18 | 0x0d500B1d8E8eF31E21C99d1Db9A6444d3ADf1270 |
| USDC | Polygon | 6 | 0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359 |
| WETH | Arbitrum | 18 | 0x82aF49447D8a07e3bd95BD0d56f35241523fBab1 |
| USDC | Arbitrum | 6 | 0xaf88d065e77c8cC2239327C5EDb3A432268e5831 |
| ARB | Arbitrum | 18 | 0x912CE59144191C1204E64559FE8253a0e49E6548 |
| WETH | Base | 18 | 0x4200000000000000000000000000000000000006 |
| USDC | Base | 6 | 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 |
| WETH | Optimism | 18 | 0x4200000000000000000000000000000000000006 |
| USDC | Optimism | 6 | 0x0b2C639c533813f4Aa9D7837CAf62653d097Ff85 |
| OP | Optimism | 18 | 0x4200000000000000000000000000000000000042 |
Native tokens (ETH, BNB, MATIC): Use module=account&action=balance, no contract address.
Quick Examples
Check ETH Balance
curl -s "https://api.etherscan.io/v2/api?module=account&action=balance&address=0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb&chainid=1&tag=latest&apikey=${API_KEY}"Get Recent Transactions
curl -s "https://api.etherscan.io/v2/api?module=account&action=txlist&address=0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb&chainid=1&page=1&offset=10&sort=desc&apikey=${API_KEY}"Check USDC Balance
curl -s "https://api.etherscan.io/v2/api?module=account&action=tokenbalance&contractaddress=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48&address=0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb&chainid=1&tag=latest&apikey=${API_KEY}"
# Returns raw integer — divide by 10^6 for USDCVerify Transaction Status
curl -s "https://api.etherscan.io/v2/api?module=transaction&action=gettxreceiptstatus&txhash=0xABC...&chainid=1&apikey=${API_KEY}"
# result.status = "1" → success, "0" → failedGet Current Gas Prices
curl -s "https://api.etherscan.io/v2/api?module=gastracker&action=gasoracle&chainid=1&apikey=${API_KEY}"
# Returns SafeGasPrice, ProposeGasPrice, FastGasPrice in GweiCritical Rules
Pagination: Always include page=1&offset=100&sort=desc on list endpoints. For "all" results, paginate until result.length < offset.
Token balances: Returned as raw integers. Divide by 10^decimals.
Time filtering: Most endpoints lack server-side time filters. Fetch results, filter by timeStamp client-side.
Errors:
status=0, empty result → wrong chain or actionmessage=NOTOK→ rate limit or invalid params- Missing recent txs → forgot pagination params
Transaction verification: Never assume finality. Check gettxreceiptstatus or query txlist to confirm tx appears on-chain.
References
Full docs: https://docs.etherscan.io/llms.txt