a) there is no MarketCap field available directly

b) price*share_count will not work. Share counts are not split adjusted. Look at the TSLA 5:1 split event between 2020-08-28 - 2020-09-01 , FinancialStatements.BalanceSheet.ShareIssued.ThreeMonths (or any other share count for that matter) stayed constant.

c) inferring from balances & valuation ratios won't work either. Look at TSLA between 2020-08-28 - 2020-09-01   ValuationRatios.PERatio  jumped from 691 to 1203 in 2 days, there's no way that's correct.

 How are people getting Market Capitalization in a reliable way in their algorithms?