What is MCP Context Middleware?
A protocol-aware intermediary that inspects, transforms, or enriches MCP traffic between clients and servers — performing functions like policy enforcement, PII redaction, logging, or tool annotation injection.
WHY IT MATTERS
MCP middleware sits in the communication path between agent and server, understanding the protocol well enough to inspect tool calls, modify responses, inject metadata, or block requests. Unlike a generic HTTP proxy, context middleware understands MCP's JSON-RPC messages and can make decisions based on tool names, arguments, and categories.
The term was introduced at MCP Dev Summit 2026 by Saxo Bank's Peder Holdgaard Pedersen, describing the enterprise need for protocol-aware intermediaries.
HOW POLICYLAYER USES THIS
PolicyLayer is MCP context middleware — it inspects every tool call, evaluates policies, and forwards or blocks based on the JSON policy attached to the grant.