Etherscan MCP Server

A Go implementation of an Etherscan API client for the Model Context Protocol (MCP) that enables LLM applications to access Etherscan blockchain data.

Features

• Access Etherscan API V2 for multi-chain support
• Use a single API key for over 50 supported chains
• Supports various blockchain data retrieval methods:
  • Account balances
  • Block information
  • Contract data (ABI, source code)
  • Gas oracle
  • Token information
  • Transaction data
  • And more

Requirements

• Etherscan API key (get from https://etherscan.io/myapikey)

Installation

1. Clone the repository:

   git clone https://github.com/huahuayu/etherscan-mcp-server.git
   cd etherscan-mcp-server
   

2. Set Etherscan API key env variable:

   ETHERSCAN_API_KEY=your_api_key_here
   

3. Build the server:

   make build
   

4. Install the server:

   make install # install to /usr/local/bin
   

Usage

Default Mode (Standard Input/Output)

Run the server using stdin/stdout communication (default mode):

./bin/etherscan-mcp-server

This mode is useful for direct integration with LLM applications that communicate via stdin/stdout.

MCP config:

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

Restart cursor and check if it's success:

SSE Mode

Run the server in Server-Sent Events mode:

./bin/etherscan-mcp-server --sse

In SSE mode, the server listens on HTTP and provides an SSE endpoint.

SSE MCP config:

{
  "mcpServers": {
    "etherscan-mcp-server": {
      "url": "http://localhost:4000/sse",
      "env": {
        "ETHERSCAN_API_KEY": "$your_api_key"
      }
    }
  }
}

Server Options

• --sse: Enable SSE server mode (default is stdin/stdout mode)
• --port <port>: Specify the port for SSE server (defaults to PORT env var or 4000)

Connection Endpoints (SSE Mode)

When running in SSE mode, the server provides:

• SSE Endpoint: http://localhost:4000/sse

Supported Chains

50+ chains supported, please refer to the Etherscan V2 Supported Chains for a complete list and their corresponding Chain IDs.

Note on Free Tier Limitations & RPC Fallback: According to Etherscan's supported chains policy, some networks are not available under the Free API plan. These include (but are not limited to):

• BNB Smart Chain (BSC) — Chain ID: 56
• Base — Chain ID: 8453
• Avalanche C-Chain — Chain ID: 43114

For these three chains, this server has a built-in RPC fallback mechanism: when the Etherscan API returns NOTOK, it automatically falls back to free public RPC endpoints using standard JSON-RPC methods. No paid plan is needed for the following tools on these chains:

Tool	JSON-RPC Method
getLatestBlockNumber	eth_blockNumber
getAccountBalance	eth_getBalance
getTokenBalance	eth_call (balanceOf)
getTokenDetails	eth_call (name/symbol/decimals)
getTransactionByHash	eth_getTransactionByHash
getTransactionReceipt	eth_getTransactionReceipt
getTransactionCount	eth_getTransactionCount
executeContractMethod	eth_call

RPC Endpoints Used:

• BSC: https://binance.llamarpc.com
• Base: https://base.llamarpc.com
• Avalanche C-Chain: `https://api.avax.network/ext/bc/C/

... View full README on GitHub