Etherscan MCP Tool

Instructions

Implementation Reference

• index.ts:351-391 (handler)

  The handler function that implements the core logic for the 'get_token_balance' tool by querying the Etherscan API for the token balance of a given address on a specific chain.

  async function handleGetTokenBalance(req: any, apiKey: string) {
      const chainId = req.params.arguments.chain_id;
      const tokenAddress = req.params.arguments.token_address;
      const address = req.params.arguments.address;
  
      try {
          const response = await axios.get(
              `https://api.etherscan.io/v2/api?chainid=${chainId}&module=account&action=tokenbalance&contractaddress=${tokenAddress}&address=${address}&tag=latest&apikey=${apiKey}`
          );
  
          if (response.data.status === "1") {
              const balance = response.data.result;
              return {
                  content: [
                      {
                          type: "text",
                          text: `Balance of token ${tokenAddress} for address ${address} on chain ${chainId}: ${balance}`,
                      },
                  ],
              };
          } else {
              return {
                  content: [
                      {
                          type: "text",
                          text: `Failed to get token balance: ${response.data.message}`,
                      },
                  ],
              };
          }
      } catch (error) {
          return {
              content: [
                  {
                      type: "text",
                      text: `Failed to get token balance: ${error}`,
                  },
              ],
          };
      }
  }

• index.ts:131-152 (schema)

  The ToolDefinition object defining the input schema, name, and description for the 'get_token_balance' tool.

  const getTokenBalance: ToolDefinition = {
      name: "get_token_balance",
      description: "Get the balance of a specific token for a specific address",
      inputSchema: {
          type: "object",
          properties: {
              chain_id: {
                  type: "integer",
                  description: "The chain ID",
              },
              token_address: {
                  type: "string",
                  description: "The address of the token",
              },
              address: {
                  type: "string",
                  description: "The address to check the balance for",
              },
          },
          required: ["chain_id", "token_address", "address"],
      },
  };

• index.ts:216-223 (registration)

  The toolDefinitions map where 'get_token_balance' is registered by including getTokenBalance in the tools object.

  const toolDefinitions: { [key: string]: ToolDefinition } = {
      [getFilteredRpcList.name]: getFilteredRpcList,
      [getChainId.name]: getChainId,
      [getTotalSupply.name]: getTotalSupply,
      [getTokenBalance.name]: getTokenBalance,
      [getTokenHolders.name]: getTokenHolders,
      [getTokenHoldersCount.name]: getTokenHoldersCount
  };

• index.ts:485-486 (registration)

  The switch case in the callToolHandler that dispatches calls to the 'get_token_balance' handler.

  case getTokenBalance.name:
      return await handleGetTokenBalance(req, apiKey);

• index.ts:509-511 (registration)

  The server capabilities section where the toolDefinitions (including 'get_token_balance') are registered with the MCP server.

  capabilities: {
      tools: toolDefinitions,
  }