bnbchain-mcp

Instructions

Implementation Reference

• src/evm/services/balance.ts:46-86 (handler)

  The core handler function that resolves addresses, fetches ERC20 balance, symbol, and decimals from the blockchain, and formats the result.

  export async function getERC20Balance(
    tokenAddressOrEns: string,
    ownerAddressOrEns: string,
    network = "ethereum"
  ): Promise<{
    raw: bigint
    formatted: string
    symbol: string
    decimals: number
    network: string
    tokenAddress: Address
    ownerAddress: Address
  }> {
    // Resolve ENS names to addresses if needed
    const tokenAddress = await resolveAddress(tokenAddressOrEns, network)
    const ownerAddress = await resolveAddress(ownerAddressOrEns, network)
  
    const publicClient = getPublicClient(network)
  
    const contract = getContract({
      address: tokenAddress,
      abi: ERC20_ABI,
      client: publicClient
    })
  
    const [balance, symbol, decimals] = await Promise.all([
      contract.read.balanceOf([ownerAddress]) as Promise<bigint>,
      contract.read.symbol() as Promise<string>,
      contract.read.decimals() as Promise<number>
    ])
  
    return {
      raw: balance,
      formatted: formatUnits(balance, decimals),
      symbol,
      decimals,
      network,
      tokenAddress,
      ownerAddress
    }
  }

• src/evm/modules/tokens/tools.ts:60-82 (registration)

  Registers the 'get_erc20_balance' MCP tool, including input schema validation with Zod and a wrapper handler that calls the core getERC20Balance service.

  server.tool(
    "get_erc20_balance",
    "Get ERC20 token balance for an address",
    {
      tokenAddress: z.string().describe("The ERC20 token contract address"),
      address: z.string().describe("The address to check balance for"),
      network: defaultNetworkParam,
      privateKey: privateKeyParam
    },
    async ({ network, tokenAddress, address, privateKey }) => {
      try {
        const res = await services.getERC20Balance(
          tokenAddress as Address,
          address || privateKeyToAccount(privateKey as Hex).address,
          network
        )
  
        return mcpToolRes.success(res)
      } catch (error) {
        return mcpToolRes.error(error, "fetching ERC20 token balance")
      }
    }
  )