eth-mcp

chenjjiaa/eth-mcp

3.1

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A MCP server built in Rust, enabling AI agents to seamlessly interact with the Ethereum blockchain.

Ethereum Trading MCP Server

Rust Tokio Ethereum Ethers.rs MCP Uniswap

A Model Context Protocol (MCP) server implemented in Rust that enables AI agents to query Ethereum balances and simulate token swaps on Uniswap.

- Get up and running quickly.

Features

The server provides three MCP tools:

  1. get_balance - Query ETH and ERC20 token balances

    • Input: wallet address, optional token contract address
    • Output: balance information with proper decimals

  2. get_token_price - Get current token price in USD and ETH

    • Input: token address (0x...) or symbol (e.g., "USDC", "WETH")
    • Output: price data from CoinGecko API

  3. swap_tokens - Simulate token swaps on Uniswap V2 or V3

    • Input: from_token, to_token, amount, slippage tolerance
    • Output: simulation result showing estimated output and gas costs
    • Note: Constructs real Uniswap transactions and simulates them using eth_call without executing on-chain

Project Structure

src/
├── main.rs          # Server entry point and transport configuration
├── server.rs        # MCP server implementation with tool handlers
├── swap.rs          # Uniswap V2/V3 swap simulation logic
└── bin/
    ├── client.rs               # MCP client for testing
    ├── test_eth_balance.rs     # Test for ETH balance queries
    ├── test_erc20_balance.rs   # Test for ERC20 balance queries
    ├── test_token_price.rs     # Test for token price queries
    └── test_swap.rs            # Test for swap simulations

Dependencies

  • Rust (latest stable version)
  • tokio - Async runtime
  • ethers-rs - Ethereum RPC client library
  • rmcp - MCP SDK for Rust
  • rust_decimal - Financial precision handling
  • tracing - Structured logging
  • reqwest - HTTP client for price API calls
  • ethabi - ABI encoding/decoding

Setup Instructions

Prerequisites

  1. Install Rust (if not already installed):

    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

  2. Clone the repository:

    git clone https://github.com/chenjjiaa/eth-mcp;
cd eth-mcp

Environment Variables

Create a .env file in the project root (or use environment variables):

# Ethereum RPC endpoint (required)
ETH_RPC_URL=https://eth.llamarpc.com
# Or use Infura/Alchemy:
# ETH_RPC_URL=https://mainnet.infura.io/v3/YOUR_API_KEY

# Server configuration (optional)
SERVER_HOST=127.0.0.1        # Default: 127.0.0.1
SERVER_PORT=0                # Default: 0 (stdio mode). Set to >0 for TCP mode

# Logging (optional)
RUST_LOG=info                 # Default: info. Options: trace, debug, info, warn, error

# Wallet address
WALLET_ADDRESS=0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045
# USDC contract addr
TOKEN_ADDRESS=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48

Note: The server defaults to stdio mode (MCP standard) when SERVER_PORT=0. For TCP mode, set SERVER_PORT to a valid port number.

Build and Run

  1. Build the project:

    cargo b
# Or for release:
cargo b --release

  2. Run the server:

    # Stdio mode (default, for MCP clients)
cargo r --bin server

# Or directly:
./target/debug/server

  3. Run tests:

    # Run all tests
cargo test

# Run specific test binaries
cargo r --bin test_eth_balance
cargo r --bin test_erc20_balance
cargo r --bin test_token_price
cargo r --bin test_swap

Example MCP Tool Calls

1. Get ETH Balance

Request:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "get_balance",
    "arguments": {
      "wallet_address": "0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb"
    }
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\n  \"wallet_address\": \"0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb\",\n  \"token_address\": null,\n  \"balance\": \"0.000000000000000000\",\n  \"decimals\": 18,\n  \"raw_balance\": \"0\"\n}"
      }
    ]
  }
}

2. Get ERC20 Token Balance

Request:

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "get_balance",
    "arguments": {
      "wallet_address": "0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb",
      "token_address": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
    }
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\n  \"wallet_address\": \"0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb\",\n  \"token_address\": \"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48\",\n  \"balance\": \"1000.000000\",\n  \"decimals\": 6,\n  \"raw_balance\": \"1000000000\"\n}"
      }
    ]
  }
}

3. Get Token Price

Request:

{
  "jsonrpc": "2.0",
  "id": 3,
  "method": "tools/call",
  "params": {
    "name": "get_token_price",
    "arguments": {
      "token": "USDC"
    }
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": 3,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\n  \"token\": \"USDC\",\n  \"token_address\": null,\n  \"price_usd\": \"1.000000\",\n  \"price_eth\": \"0.000300\",\n  \"last_updated\": null\n}"
      }
    ]
  }
}

4. Simulate Token Swap

Request:

{
  "jsonrpc": "2.0",
  "id": 4,
  "method": "tools/call",
  "params": {
    "name": "swap_tokens",
    "arguments": {
      "from_token": "ETH",
      "to_token": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
      "amount": "1.0",
      "slippage_tolerance": "0.5",
      "version": "v2"
    }
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": 4,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "{\n  \"from_token\": \"ETH\",\n  \"to_token\": \"0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48\",\n  \"input_amount\": \"1.0\",\n  \"estimated_output\": \"3200.123456\",\n  \"minimum_output\": \"3184.122842\",\n  \"slippage_tolerance\": \"0.5\",\n  \"estimated_gas\": \"150000\",\n  \"estimated_gas_eth\": \"0.003000\",\n  \"price_impact\": null,\n  \"involves_eth\": true,\n  \"version\": \"v2\"\n}"
      }
    ]
  }
}

Design Decisions

  1. MCP Protocol Implementation: Used the rmcp SDK to handle MCP protocol communication, which provides type-safe tool registration and request/response handling. The server supports both stdio (standard MCP mode) and TCP transport for flexibility.

  2. Ethereum Interaction: Leveraged ethers-rs for Ethereum RPC interactions, using direct eth_call for ERC20 balance queries and swap simulations. This approach ensures we're working with real on-chain data without requiring transaction signing for read operations.

  3. Financial Precision: Used rust_decimal throughout the codebase for all financial calculations to avoid floating-point precision errors. All token amounts are handled with proper decimal places based on the token's decimals field.

  4. Swap Simulation: For swap operations, the implementation constructs real Uniswap V2/V3 transactions and simulates them using eth_call (via provider.call()), which executes the transaction locally without broadcasting it to the network. This provides accurate estimates including gas costs without requiring actual transaction execution.

  5. Price Data: Integrated CoinGecko API for token price data, supporting both contract addresses and symbol lookups. The implementation handles common token symbols and provides fallback mechanisms for price queries.

Known Limitations and Assumptions

  1. Ethereum Mainnet Only: The server is currently configured for Ethereum mainnet. Support for testnets (Goerli, Sepolia) would require additional configuration and potentially different Uniswap router addresses.

  2. Price API Dependency: Token price queries depend on CoinGecko's free API, which has rate limits. High-frequency queries may hit rate limits, and the API may not support all tokens.

  3. Uniswap Router Addresses: The implementation uses hardcoded Uniswap V2 and V3 router addresses for mainnet. Different networks or future router upgrades would require code changes.

  4. Gas Estimation: Gas estimates are approximate and based on transaction simulation. Actual gas costs may vary depending on network conditions at execution time.

  5. No Wallet Management or Transaction Signing: The server only simulates swaps and does not execute them on-chain. Wallet management, private key handling, and transaction signing functionality are not implemented. The server cannot sign or broadcast transactions to the blockchain.

  6. Slippage Calculation: Minimum output calculation uses simple percentage-based slippage. More sophisticated slippage models (e.g., dynamic slippage based on pool liquidity) are not implemented.

  7. Price Impact: Price impact calculation is not fully implemented for all swap scenarios, especially for large trades that might affect pool prices.

TODO / Future Improvements

Changelog

License

This project is licensed under the .