Introduction: 2026 – Data Interfaces Are Undergoing a "Paradigm Shift" With the proliferation of AI trading agents and quantitative strategies in 2026, the role of financial data APIs has fundamentally changed. They are no longer mere "data carriers" but have become the "eyes" of trading strategies. In the selection environment of 2026, we no longer just discuss "does it have a REST API" or "does it provide a Python SDK". The real battleground has shifted to : MCP (Model Context Protocol) Support : Can AI agents (e.g., Claude, custom GPTs) directly call the API to get real-time market data using natural language? WebSocket Robustness : For T+0 instruments like forex and precious metals, are native reconnection and keep-alive mechanisms supported? Unified Cross-Asset Access : Can you fetch U.S. stocks, A-shares, gold (XAU/USD), and GBP data with a single interface? This article provides a hardcore comparative analysis of mainstream financial market data APIs based on the latest 2026 data. 1.…