Ethereum Trading MCP Server

An MCP server built in Rust to interact with the Ethereum blockchain.

Features

• get_balance: Query ETH and ERC20 token balances with proper decimal formatting.
• get_token_price: Get current token price in USD. Supports ETH via Chainlink and arbitrary tokens via Uniswap V3 (decimal-correct).
• swap_tokens: Simulate Uniswap V3 swaps, calculate minimum output with slippage, construct router calldata, and perform a read-only eth_call on the router.

Prerequisites

• Rust (latest stable)
• An Ethereum RPC URL (e.g., from Alchemy or Infura)
• A private key (for signing transactions/simulations)

Setup

1. Clone the repository.
2. Copy .env.example to .env:

   cp .env.example .env
   

3. Edit .env and set your ETHEREUM_RPC_URL and PRIVATE_KEY.

Usage

Building

cargo build --release

Running

The server uses Stdio for MCP communication.

cargo run

Example MCP Tool Calls

get_balance

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "get_balance",
    "arguments": {
      "address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
      "token_address": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
    }
  },
  "id": 1
}

get_token_price (Arbitrary Token)

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "get_token_price",
    "arguments": {
      "token_symbol": "UNI",
      "token_address": "0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984"
    }
  },
  "id": 2
}

swap_tokens (Simulation & Construction)

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "swap_tokens",
    "arguments": {
      "from_token": "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2", 
      "to_token": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
      "amount": "1000000000000000000",
      "slippage_tolerance": 0.5
    }
  },
  "id": 3
}

Design Decisions

• Client choice: Alloy is used for its performance, strong typing, and lack of heavy codegen requirements.
• Async/runtime: Tokio + async everywhere to match RPC-bound workloads; tools are Send + Sync for concurrent handling.
• Precision: rust_decimal is used end-to-end for price/balance math to avoid float drift; Q96 is a fixed decimal constant to prevent overflow.
• Uniswap V3: Selected to cover the majority of mainnet liquidity and fee tiers efficiently.
• Swap simulation: Two-step process: QuoterV2 eth_call for amounts/gas, followed by a router eth_call with real calldata to surface approval/funding issues.
• Calldata exposure: swap_tokens returns router calldata so agents can sign/broadcast; simulation is read-only.
• Decimals handling: ERC20 decimals() fetched for price/balance; 10^decimals built with decimal-safe helper to avoid overflow.
• MCP shape: Hybrid response (content for strict MCP, data for structured consumption) to maximize compatibility and programmatic usability.
• Error transparency: Router simulation errors are bubbled back in router_call_simulation instead of being swallowed.
• Scope: Focused on Uniswap V3 and ERC20-to-ERC20 swaps.

Limitations

• Gas Estimation: The returned gas estimate is for the simulation (Quoter) and may differ from the actual swap transaction gas.
• Price Impact: The price tool calculates spot price from slot0 and does not account for price impact of large trades (though swap_tokens simulation does).
• Approvals/Funding: Router eth_call may revert if the signer lacks allowances or balance; this is surfaced in the response but not auto-resolved.
• Coverage: Only Uniswap V3 path is implemented (no V2), and swaps assume ERC20->ERC20 (ETH wrapping/unwrapping not included).

Error Response Examples

Router simulation revert (missing allowance/balance)

{
  "jsonrpc": "2.0",
  "result": {
    "content": [{ "type": "text", "t

... [View full README on GitHub](https://github.com/maybleeess-collab/MCP-server-built-in-Rust-to-interact-with-the-Ethereum-blockchain#readme)