Microsoft's P/E ratio on the same day ranged from 28.93 to 34.4 depending on the source; all correct, all using different methods, most undisclosed. FinanceToolkit fixes this. It's an open-source Python library with 200+ financial metrics where every formula is fully transparent and documented. No black boxes, no required paid-subscription methodology, no conflicting definitions across sources. Also has a MCP server attached!