0x Price/Quote API doesn't handle different token decimals correctly

Question

I am using the 0x Price and Quote API for my project and encountered the following Problem which could be a bug in the API.

Example request: https://api.0x.org/swap/v1/quote?sellToken=0x514cdb9cd8a2fb2bdcf7a3b8ddd098caf466e548&buyToken=0x95ad61b0a150d79219dcf64e1e6cc01f0b64c4ce&sellAmount=91852168466729

Token Decimals:

• 0x514cdb9cd8a2fb2bdcf7a3b8ddd098caf466e548 has 9 Decimals
• 0x95ad61b0a150d79219dcf64e1e6cc01f0b64c4ce has 18 Decimals

The response includes the following values among others:

• "buyAmount": "17621716298148718"
• "sellAmount": "91852168466729"
• "sellTokenToEthRate": "681573019064660.96173915"
• "buyTokenToEthRate": "131484453.43337870913186545"

sellAmount is corrently based on 9 Decimals --> sellAmount / sellTokenToEthRate = 0.13476497146 ETH which is correct.

However buyAmount is also based on 9 Decimals --> buyAmount / buyTokenToEthRate = 134141724.605 which is not correct and 9 decimals off the correct value.

Is this a know issue or am I doing something wrong here? Appreciate the help!

Answer 1

As temporary workaround I'm using a multiplier for calculating the eth value of the buyAmount:

const sellTokenToBuyTokenDecimalMultiplier: BigDecimal = 
  new BigDecimal(`1e${sellTokenDecimals}`,)
    .divide(new BigDecimal(`1e${buyTokenDecimals}`), 19);

const buyValueInEth: BigDecimal = 
      new BigDecimal(buyAmount.toString())
        .divide(buyTokenToEthRate, 18)
        .multiply(sellTokenToBuyTokenDecimalMultiplier);

(Hint: BigDecimal is https://www.npmjs.com/package/js-big-decimal)