EVM MCP Server

Instructions

Implementation Reference

• src/index.ts:797-846 (handler)

  Full implementation of the 'eth_chainId' MCP tool handler. Registers the tool with no input parameters and provides an async handler that calls the 'eth_chainId' RPC method via makeRPCCall, parses the hex result to decimal, maps it to a known chain name, and returns a formatted text response.

  server.tool(
    "eth_chainId",
    "Returns the chain ID of the current network",
    {},
    async () => {
      try {
        const result = await makeRPCCall("eth_chainId");
        const chainId = parseInt(result, 16);
  
        const chainNames: { [key: number]: string } = {
          1: "Ethereum Mainnet",
          11155111: "Sepolia Testnet",
          5: "Goerli Testnet",
          137: "Polygon Mainnet",
          80001: "Polygon Mumbai Testnet",
          42161: "Arbitrum One",
          421614: "Arbitrum Sepolia",
          10: "Optimism",
          420: "Optimism Sepolia",
          56: "BNB Smart Chain",
          97: "BNB Smart Chain Testnet",
        };
  
        return {
          content: [
            {
              type: "text",
              text: formatResponse(
                {
                  chain_id_hex: result,
                  chain_id_decimal: chainId,
                  chain_name: chainNames[chainId] || "Unknown Network",
                },
                "Network Chain ID",
              ),
            },
          ],
        };
      } catch (error: any) {
        return {
          content: [
            {
              type: "text",
              text: `Error: ${error.message}`,
            },
          ],
        };
      }
    },
  );

• src/index.ts:89-96 (helper)

  Generic helper function used by eth_chainId (and other tools) to perform RPC calls to the Ethers provider.

  async function makeRPCCall(method: string, params: any[] = []): Promise<any> {
    try {
      const result = await provider.send(method, params);
      return result;
    } catch (error: any) {
      throw new Error(`RPC call failed: ${error.message}`);
    }
  }