MCP Is Not Replacing REST. It Is Replacing the Entire Mental Model of How Agents Use Tools.
REST was designed for humans writing code to call services. You read the docs, you write the client, you ship it. That whole loop assumes a developer is in the middle, translating intent into HTTP calls. When you put an LLM in the driver's seat, that assumption breaks completely, and the cracks are showing up in every agent system I have seen in production.
What Actually Happened
Model Context Protocol (MCP), originally introduced by Anthropic, has crossed from "interesting spec" to "actual adoption pressure" faster than most protocol transitions I have watched. The pattern is now visible across the ecosystem: Cognizant just expanded their Anthropic partnership specifically to bring Claude-powered agents to enterprise workflows, and when you look at what those workflows require, MCP is not optional. You cannot bolt REST onto an agent loop and call it done.
The short version of what MCP is: a standardized, bidirectional protocol that lets LLMs discover, negotiate, and invoke tools without a human writing a custom client for each integration. The server advertises its capabilities. The model reads them. The model calls them. No glue code, no prompt-stuffed API docs, no fragile JSON schema passed in a system prompt and hoped for the best.
