Arbitrum MCP Server

Instructions

Implementation Reference

• src/index.ts:252-268 (handler)

  MCP tool handler for 'get_balance_ether': resolves RPC URL, instantiates EthereumAccountClient, calls getBalanceInEther on the provided address, formats response as text content.
  case "get_balance_ether": { const rpcUrl = await this.resolveRpcUrl( (args.rpcUrl as string) || (args.chainName as string) ); const ethereumAccountClient = new EthereumAccountClient(rpcUrl); const balanceEth = await ethereumAccountClient.getBalanceInEther( args.address as string ); return { content: [ { type: "text", text: `Balance: ${balanceEth} ETH`, }, ], }; }
• src/index.ts:962-980 (registration)

  Tool registration definition in getAvailableTools(): specifies name 'get_balance_ether', description, and input schema requiring 'address' (rpcUrl and chainName optional). Used for list tools response.
  { name: "get_balance_ether", description: "Get balance of an address in ETH", inputSchema: { type: "object" as const, properties: { rpcUrl: { type: "string", description: "The RPC URL of the chain (optional if default is set)", }, address: { type: "string", description: "Ethereum address to check balance for", }, }, required: ["address"], }, },
• src/index.ts:965-979 (schema)

  Input schema definition for 'get_balance_ether' tool: object with optional rpcUrl/chainName and required address string.
  inputSchema: { type: "object" as const, properties: { rpcUrl: { type: "string", description: "The RPC URL of the chain (optional if default is set)", }, address: { type: "string", description: "Ethereum address to check balance for", }, }, required: ["address"], },
• src/clients/ethereum-account-client.ts:41-53 (helper)

  Primary helper implementation: getBalanceInEther(address) converts wei balance to human-readable ETH string, handling integer and decimal cases precisely.
  async getBalanceInEther(address: string): Promise<string> { const weiBalance = await this.getBalance(address); const wei = BigInt(weiBalance); const ether = wei / BigInt('1000000000000000000'); const remainder = wei % BigInt('1000000000000000000'); if (remainder === BigInt(0)) { return ether.toString(); } else { const etherDecimal = Number(wei) / 1e18; return etherDecimal.toFixed(6).replace(/\.?0+$/, ''); } }
• src/clients/ethereum-account-client.ts:36-39 (helper)

  Supporting helper: getBalance(address) performs raw 'eth_getBalance' RPC call at latest block, returns wei hex string.
  async getBalance(address: string): Promise<string> { const balance = await this.makeRpcCall('eth_getBalance', [address, 'latest']); return balance; }