Ethereum RPC MCP Server

Instructions

Implementation Reference

• index.js:112-132 (handler)

  The handler function for the 'eth_getCode' tool. It makes an RPC call using makeRpcCall to retrieve the bytecode at the specified address and block parameter, then formats the response text accordingly, indicating if it's a contract or not.

  async (args) => {
    try {
      console.error(`Getting code for address: ${args.address} at block: ${args.blockParameter}`);
      
      const code = await makeRpcCall('eth_getCode', [args.address, args.blockParameter]);
      
      return {
        content: [{ 
          type: "text", 
          text: code === '0x' ? 
            `No code found at address ${args.address} (this may be a regular wallet address, not a contract)` : 
            `Contract code at ${args.address}:\n${code}`
        }]
      };
    } catch (error) {
      return {
        content: [{ type: "text", text: `Error: Failed to get code. ${error.message}` }],
        isError: true
      };
    }
  }

• index.js:109-111 (schema)

  Zod schema defining the input parameters for the 'eth_getCode' tool: 'address' (required, valid Ethereum address) and 'blockParameter' (optional, defaults to 'latest').

    address: z.string().regex(/^0x[a-fA-F0-9]{40}$/).describe('The Ethereum address to get code from'),
    blockParameter: z.string().default('latest').describe('Block parameter (default: "latest")')
  },

• index.js:105-133 (registration)

  Registration of the 'eth_getCode' tool on the MCP server using server.tool(), specifying name, description, input schema, and handler function.

  server.tool(
    'eth_getCode',
    'Retrieves the code at a given Ethereum address',
    {
      address: z.string().regex(/^0x[a-fA-F0-9]{40}$/).describe('The Ethereum address to get code from'),
      blockParameter: z.string().default('latest').describe('Block parameter (default: "latest")')
    },
    async (args) => {
      try {
        console.error(`Getting code for address: ${args.address} at block: ${args.blockParameter}`);
        
        const code = await makeRpcCall('eth_getCode', [args.address, args.blockParameter]);
        
        return {
          content: [{ 
            type: "text", 
            text: code === '0x' ? 
              `No code found at address ${args.address} (this may be a regular wallet address, not a contract)` : 
              `Contract code at ${args.address}:\n${code}`
          }]
        };
      } catch (error) {
        return {
          content: [{ type: "text", text: `Error: Failed to get code. ${error.message}` }],
          isError: true
        };
      }
    }
  );

• index.js:84-102 (helper)

  Helper function 'makeRpcCall' used by the eth_getCode handler to perform the actual Ethereum JSON-RPC call to eth_getCode.

  async function makeRpcCall(method, params = []) {
    try {
      const response = await axios.post(ETH_RPC_URL, {
        jsonrpc: '2.0',
        id: 1,
        method,
        params
      });
  
      if (response.data.error) {
        throw new Error(`RPC Error: ${response.data.error.message}`);
      }
  
      return response.data.result;
    } catch (error) {
      console.error(`Error making RPC call to ${method}:`, error.message);
      throw error;
    }
  }