What is MCP (Model Context Protocol)? Complete 2026 Guide
TL;DR — Model Context Protocol (MCP) is an open JSON-RPC 2.0 specification, introduced by Anthropic in late 2024, that lets AI agents talk to external systems — file systems, databases, APIs, custom services — through a single standardized interface. An MCP server exposes capabilities (tools, resources, and prompts); an MCP client (Claude Desktop, Cursor, Zed, Sourcegraph Cody, your own agent) consumes them. Write the server once, and every MCP-compatible client can use it — no per-app integration work.
If you have built agent tooling before, think of MCP as "LSP for AI tools": the same idea that unified language servers across editors, now applied to the plumbing between agents and the systems they need to act on.
Why MCP Exists
Before MCP, every agent framework defined its own tool format. A tool written for LangChain didn’t work in Claude Desktop, which didn’t work in your custom agent, which didn’t work in Cursor. Each integration was bespoke, every prompt-engineered "function description" was framework-specific, and every team rebuilt the same wheel.
