web3-mcp-server

Instructions

Implementation Reference

• src/tools/FetchBalance.ts:12-26 (handler)

  The main handler function that fetches the balance for a given wallet address on a specified chain using viem client.

  export const fetchBalance = async (options: FetchBalanceOptions) => {
    const { walletAddress, chainId } = options;
  
    const chain = getChainById(chainId);
    const client = createClient(chain);
  
    const balance = await client.getBalance({
      address: walletAddress as `0x${string}`,
    });
  
    return {
      balance: balance.toString(),
      formattedBalance: formatUnits(balance, chain.nativeCurrency.decimals),
    };
  };

• src/tools/FetchBalance.ts:6-9 (schema)

  Zod schema defining the input options for the fetch_balance tool: walletAddress and chainId.

  export const FetchBalanceSchema = z.object({
    walletAddress: z.string().startsWith("0x"),
    chainId: z.number(),
  });

• src/index.ts:36-38 (registration)

  Tool registration in the listTools handler, specifying name, description, and input schema.

  name: "fetch_balance",
  description: "Get the balance of a wallet",
  inputSchema: z.toJSONSchema(FetchBalanceSchema),

• src/index.ts:84-102 (registration)

  Dispatch handler in callToolRequest that parses arguments with schema and invokes the fetchBalance function, formatting the response.

  case "fetch_balance": {
    const args = FetchBalanceSchema.parse(request.params.arguments);
    const result = await fetchBalance(args);
  
    return {
      content: [
        {
          type: "text",
          text: result.balance,
          description: "The balance of the wallet",
        },
        {
          type: "text",
          text: result.formattedBalance,
          description: "The formatted balance of the wallet",
        },
      ],
    };
  }