# Etherscan > Query block explorer APIs (Etherscan, BSCScan, Polygonscan, etc.) for transactions, contracts, and gas data. Use when this capability is needed. - Skill: `tomevault-io/etherscan` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/etherscan` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/etherscan/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/etherscan --- # Multi-chain Explorer API Query Etherscan-compatible block explorer APIs for transaction history, contract source code, ABIs, and gas data. ## Supported Explorers | Chain | Base URL | Env Var (optional override) | | -------- | ----------------------------------------- | ----------------------------- | | Ethereum | `https://api.etherscan.io/api` | `ETHERSCAN_API_KEY` | | BSC | `https://api.bscscan.com/api` | `BSCSCAN_API_KEY` or same key | | Polygon | `https://api.polygonscan.com/api` | `POLYGONSCAN_API_KEY` | | Arbitrum | `https://api.arbiscan.io/api` | `ARBISCAN_API_KEY` | | Optimism | `https://api-optimistic.etherscan.io/api` | `OPTIMISM_API_KEY` | | Base | `https://api.basescan.org/api` | `BASESCAN_API_KEY` | All explorers accept the `apikey` parameter. Many share a single Etherscan key, but some chains require separate registration. **Rate limit**: 5 calls/second per key. ## Modules & Actions ### Account — Transaction History ``` ?module=account&action=txlist&address={addr}&startblock=0&endblock=99999999&page=1&offset=20&sort=desc&apikey={key} ``` Returns normal transactions for an address. ### Account — Token Transfers (ERC-20) ``` ?module=account&action=tokentx&address={addr}&page=1&offset=20&sort=desc&apikey={key} ``` Filter by contract: add `&contractaddress={token}` ### Account — ERC-721 Transfers ``` ?module=account&action=tokennfttx&address={addr}&page=1&offset=20&sort=desc&apikey={key} ``` ### Account — Balance ``` ?module=account&action=balance&address={addr}&tag=latest&apikey={key} ``` Returns balance in wei. Divide by 1e18 for ETH/BNB. ### Contract — Get ABI ``` ?module=contract&action=getabi&address={addr}&apikey={key} ``` Returns the contract ABI as a JSON string. **Tip**: Parse the result and pass it to `read_contract` or `write_contract` for dynamic contract interaction. ### Contract — Get Source Code ``` ?module=contract&action=getsourcecode&address={addr}&apikey={key} ``` Returns source code, compiler version, constructor arguments, and proxy implementation address if applicable. ### Gas Tracker (Ethereum only) ``` ?module=gastracker&action=gasoracle&apikey={key} ``` Returns SafeGasPrice, ProposeGasPrice, FastGasPrice in gwei. ## Workflow: Dynamic Contract Interaction 1. User provides a contract address 2. Call `getabi` to fetch the ABI 3. Parse the ABI to list available read/write functions 4. Use `read_contract` with the ABI and function name to query 5. Use `write_contract` for state-changing calls (with user confirmation) This enables interacting with ANY verified contract without pre-built tools. ## Usage Notes - Always include `&apikey={key}` — requests without it are heavily rate-limited - Use `offset` and `page` for pagination; don't fetch more than needed - The `getabi` endpoint only works for verified contracts - For proxy contracts, `getsourcecode` includes the implementation address — fetch that ABI too - Cross-reference contract data with `security-check` skill for risk assessment ## Example Queries User: "Show my recent transactions on BSC" → Call BSCScan `txlist` for active wallet, present last 10 with value and status User: "Get the ABI for this contract: 0x..." → Call `getabi`, parse result, summarize available functions User: "What's the current gas price on Ethereum?" → Call `gasoracle`, present safe/standard/fast prices --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/termix-official) — claim your Tome and manage your conversions.