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, }