Introduction: Why Do We Need a Unified API? If you've worked on financial data development, you've likely experienced this scenario: checking A-share prices requires connecting to East Money or Tushare, Hong Kong stocks need LongBridge or Futu, US stocks require Polygon.io or Yahoo Finance, and forex and precious metals demand OANDA or other data sources. Before your project is even finished, you've already collected a full set of API keys, with each interface having different data formats—just mapping fields can take days. In reality, while A-shares, Hong Kong stocks, US stocks, forex, and precious metals all belong to price discovery instruments in terms of financial attributes, their API design logic naturally has huge gaps due to fundamental differences in trading rules, data sources, and technical architecture.…