@supernova123/etherscan-mcp-server

Etherscan MCP Server

An MCP server for Etherscan — connect any MCP-compatible client to the Ethereum blockchain explorer.

What is this?

An MCP (Model Context Protocol) server that gives AI assistants and agents access to Etherscan's Ethereum blockchain explorer API — ETH balances, ERC-20 token balances, transaction history, contract ABIs, and gas prices — through natural language.

Use it with Claude Desktop, Cursor, Windsurf, Cline, Continue, or any MCP-compatible client to inspect wallets, audit contracts, and analyze on-chain activity.

Why use this?

• No API key required — works out of the box with Etherscan's free tier (limited to ~1 call/5s without a key)
• Optional API key support — set ETHERSCAN_API_KEY for 5 calls/sec and full results
• 8 built-in tools — covers the most common on-chain queries
• Clean markdown output — results read naturally in chat
• Rate-limited automatically — respects free tier limits, retries on 429

Tools

Tool	Description
get_eth_balance	Get native ETH balance for an address
get_token_balances	Get all ERC-20 token balances for an address
get_transaction	Get full details for a transaction by hash
get_transactions_by_address	Get normal (external) transactions for an address
get_erc20_transfers	Get ERC-20 token transfer events for an address
get_internal_transactions	Get internal (contract-called) transactions for an address
get_contract_abi	Get the ABI for a verified smart contract
get_gas_price	Get current gas price oracle (slow/standard/fast in Gwei)

Quick Start

1. Add to your MCP client

Add this to your MCP client config (e.g. claude_desktop_config.json):

{
  "mcpServers": {
    "etherscan": {
      "command": "npx",
      "args": ["-y", "etherscan-mcp-server"]
    }
  }
}

That's it. npx downloads and runs it automatically. For higher rate limits, get a free API key at etherscan.io/apis and add it:

{
  "mcpServers": {
    "etherscan": {
      "command": "npx",
      "args": ["-y", "etherscan-mcp-server"],
      "env": {
        "ETHERSCAN_API_KEY": "your_key_here"
      }
    }
  }
}

2. Use it

Ask your AI assistant things like:

• "What's the ETH balance of vitalik.eth's address 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045?"
• "Show me the ERC-20 token balances for that address"
• "Get details for transaction 0x..."
• "List the last 20 normal transactions for this address"
• "Show me all USDT transfers to this wallet"
• "Fetch the ABI for the USDC contract 0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48"
• "What are current gas prices on Ethereum mainnet?"

Example Output

get_eth_balance

ETH Balance for 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045

247.3821 ETH

get_gas_price

⛽ Etherscan Gas Price Oracle

- Safe Low (🐢): 12.50 Gwei
- Standard (🚗): 15.20 Gwei
- Fast (🚀): 18.90 Gwei

- Last Block: 19850000
- Gas Used Ratio: 0.512
- Suggested Base Fee: 13.40 Gwei

*Estimated tx cost for 21,000 gas: 🐢 0.000263 ETH | 🚀 0.000397 ETH*

get_transactions_by_address

Normal Transactions for 0xd8dA...6045 (20 results, page 1)

- ✅ ↗ OUT 0.5 ETH · transfer — block 19,850,123 — 2026-06-05 — gas: 15.20 Gwei — hash: 0x4f8a2b9c3d1e5f7a...
- ✅ ↙ IN 1.2 ETH · transfer — block 19,849,876 — 2026-06-05 — gas: 14.80 Gwei — hash: 0x9c1d4e7f2a8b6c3d...
- ❌ ↗ OUT 0.0 ETH · swapExactTokensForETH — block 19,849,500 — 2026-06-05 — gas: 22.10 Gwei — hash: 0x2b7c9e1f4a3d8b5c...

get_contract_abi

Contract ABI for 0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48

- Functions: 28
- Events: 13
- Constructors: 1
- Fallback/Receive: 0

### Functions (showing first 25)
  - `name()` → string (view)
  - `symbol()` → string (view)
  - `decimals()` → uint8 (view)
  - `totalSupply()` → uint256 (view)
  - `balanceOf(address)` → uint256 (view)
  - `transfer(address,uint256)` → bool (nonpayable)
  - `approve(address,uint256)` → bool (nonpayable)
  - `transferFrom(address,address,uint256)` → bool (nonpayable)
  ...

Use Cases

Wallet Inspection

"Check the ETH and token balances of this address" — get a snapshot of any wallet's holdings in seconds. Works with any Ethereum address, including smart contract wallets and multisigs.

Transaction Forensics

"Show me the last 20 transactions for this address" — trace on-chain activity, identify counterparties, and understand fund flows. Use get_internal_transactions for contract calls and get_erc20_transfers for token movements.

Smart Contract Analysis

"Get the ABI for the Uniswap Router contract" — fetch verified contract ABIs to understand what functions are available. Essential for debugging failed transactions or understanding how a protocol works.

Gas Optimization

"What are current gas prices?" — get slow/standard/fast gas estimates with projected transaction costs. Time your transactions to save on fees.

DeFi Portfolio Tracking

"Show me all token balances for my wallet" — aggregate holdings across ERC-20 tokens. Combine with get_prices from the CoinGecko MCP server for full portfolio valuation.

Security Auditing

"List all internal transactions for this contract" — trace internal calls to understand contract behavior. Useful for identifying unusual patterns or verifying that a contract does what it claims.

Security

• No API key required — works with Etherscan's free tier. Optional API key for higher rate limits.
• Read-only — only fetches public blockchain data from Etherscan's API. No writes, no mutations.
• No local file access — does not read or write any files on your machine.
• No shell access — does not execute commands or spawn processes.
• Rate-limited — automatically caps requests to stay within free tier limits.
• Open source — MIT licensed. Inspect the code at GitHub.

Troubleshooting

"API key required" or very slow responses

Without an API key, Etherscan limits you to 1 call per 5 seconds. Get a free key at etherscan.io/apis and set the ETHERSCAN_API_KEY environment variable for 5 calls/sec.

"Rate limit exceeded" (429)

The server auto-retries on 429, but rapid queries can still hit limits. With a free API key, you get 5 calls/sec. Space requests ~200ms apart for best results.

"Contract not found" or empty ABI

Only verified contracts have ABIs on Etherscan. If a contract isn't verified, the API returns an error. Check the contract's verification status on etherscan.io first.

Server won't start

Make sure Node.js 18+ is installed: node --version. If using npx, ensure npm is up to date: npm install -g npm@latest.

MCP client can't connect

Verify the config path is correct. Claude Desktop uses ~/Library/Application Support/Claude/claude_desktop_config.json on macOS and %APPDATA%\Claude\claude_desktop_config.json on Windows. Restart the client after config changes.

"Address checksum" errors

Etherscan expects checksummed addresses (mixed case). The server handles this automatically, but if you see errors, try the checksummed version from etherscan.io.

Requirements

• Node.js 18+
• Etherscan API key (recommended) — get a free one at etherscan.io/apis

Rate Limits

The server automatically rate-limits requests to ~4 calls/second to stay within Etherscan's free tier (5 calls/sec). Without an API key, Etherscan limits you to 1 call/5 seconds.

To use a higher limit, sign up for a free Etherscan API key and set the ETHERSCAN_API_KEY environment variable:

{
  "mcpServers": {
    "etherscan": {
      "command": "etherscan-mcp-server",
      "env": {
        "ETHERSCAN_API_KEY": "your_key_here"
      }
    }
  }
}

Development

git clone https://github.com/nova/etherscan-mcp-server.git
cd etherscan-mcp-server
npm install
npm run build
npm start

License

MIT