MCP Ethers Wallet

Instructions

Implementation Reference

• src/tools/erc20.ts:223-261 (handler)

  The handler function executing the erc20_balanceOf tool logic. Maps input parameters, retrieves the ERC20 token balance and symbol using EthersService, formats a user-friendly response.

  async (params) => {
    // Map deprecated parameters
    const mapped = mapParameters(params);
    
    try {
      const contractAddr = mapped.contractAddress || params.tokenAddress;
      if (!contractAddr) {
        throw new Error('Either contractAddress or tokenAddress must be provided');
      }
      const balance = await ethersService.getERC20Balance(
        mapped.ownerAddress,
        contractAddr,
        mapped.provider,
        mapped.chainId
      );
      
      // Get token info to format the response
      const tokenInfo = await ethersService.getERC20TokenInfo(
        contractAddr,
        mapped.provider,
        mapped.chainId
      );
      
      return {
        content: [{ 
          type: "text", 
          text: `${mapped.ownerAddress} has a balance of ${balance} ${tokenInfo.symbol}`
        }]
      };
    } catch (error) {
      return {
        isError: true,
        content: [{ 
          type: "text", 
          text: `Error getting token balance: ${error instanceof Error ? error.message : String(error)}`
        }]
      };
    }
  }

• src/tools/erc20.ts:214-222 (schema)

  Input schema validation for the erc20_balanceOf tool using Zod, defining parameters like contractAddress, ownerAddress, provider, and chainId.

  {
    contractAddress: contractAddressSchema,
    tokenAddress: tokenAddressSchema.optional(),  // Deprecated
    ownerAddress: z.string().describe(
      "The Ethereum address whose balance to check"
    ),
    provider: providerSchema,
    chainId: chainIdSchema
  },

• src/tools/erc20.ts:212-261 (registration)

  Direct MCP server.tool registration for the erc20_balanceOf tool, including description, schema, and inline handler.

  "erc20_balanceOf",
  "Get the ERC20 token balance for a specific address. Alternative naming for compatibility with MCP client tests.",
  {
    contractAddress: contractAddressSchema,
    tokenAddress: tokenAddressSchema.optional(),  // Deprecated
    ownerAddress: z.string().describe(
      "The Ethereum address whose balance to check"
    ),
    provider: providerSchema,
    chainId: chainIdSchema
  },
  async (params) => {
    // Map deprecated parameters
    const mapped = mapParameters(params);
    
    try {
      const contractAddr = mapped.contractAddress || params.tokenAddress;
      if (!contractAddr) {
        throw new Error('Either contractAddress or tokenAddress must be provided');
      }
      const balance = await ethersService.getERC20Balance(
        mapped.ownerAddress,
        contractAddr,
        mapped.provider,
        mapped.chainId
      );
      
      // Get token info to format the response
      const tokenInfo = await ethersService.getERC20TokenInfo(
        contractAddr,
        mapped.provider,
        mapped.chainId
      );
      
      return {
        content: [{ 
          type: "text", 
          text: `${mapped.ownerAddress} has a balance of ${balance} ${tokenInfo.symbol}`
        }]
      };
    } catch (error) {
      return {
        isError: true,
        content: [{ 
          type: "text", 
          text: `Error getting token balance: ${error instanceof Error ? error.message : String(error)}`
        }]
      };
    }
  }

• src/tools/index.ts:24-24 (registration)

  Top-level registration call to registerERC20Tools, which registers the erc20_balanceOf tool among others.

  registerERC20Tools(server, ethersService);