MCP is one of the most thoughtfully scoped technical standards to come out of the AI ecosystem. That scope is intentional. Understanding exactly where MCP stops is the precondition for understanding what needs to be built on top of it. This post is about that boundary. What MCP actually does MCP is a JSON-RPC 2.0 protocol that defines three primitives a server can expose: tools, resources, and prompts. It turns the N x M integration problem between LLM applications and external tools into N + M. Build a server once, and any compliant client can use it. The adoption numbers are striking. In sixteen months, MCP crossed 110 million monthly SDK downloads and more than 10,000 community-built server implementations. Every major AI vendor now supports it. In December 2025, Anthropic donated MCP to the Agentic AI Foundation under the Linux Foundation, co-founded with Block and OpenAI. In April 2026, the AAIF held the MCP Dev Summit North America in New York City with 1,200 attendees, double the previous summit.…