APEX Protocol introduces an open standard for AI agent trading, defining how autonomous agents communicate with brokers, exchanges, and execution venues. The protocol specification includes 19 mandatory tools across five domains — session, account, orders, market data, and risk — plus a realtime resource model with live state, notifications, and production capability profiles.

Built on MCP over HTTP/SSE, APEX provides a vendor-neutral framework that eliminates per-broker API integrations. The protocol features a universal instrument taxonomy where identifiers like APEX:FX:EURUSD mean the same thing at every broker, solving the persistent problem of inconsistent symbol mapping across trading platforms. With 167 executable conformance checks across four reference implementations, the standard ensures protocol compliance from basic tool testing to production readiness.

APEX includes autonomous safety mechanisms like kill switches, position limits, and stale-data rejection that halt trading before models make decisions. The protocol supports multi-asset classes including FX, CFDs, crypto, and derivatives, with production profiles for both realtime and autonomous execution. Licensed under CC-BY 4.0 with Apache 2.0 reference implementations, APEX aims to become the HTTP/SSE equivalent of FIX Protocol for the AI trading era, enabling agent developers to write once and trade on any broker.