MCP (Model Context Protocol)
establishedSettled. Documented by a primary source and not seriously disputed.
An open standard for connecting AI applications to external systems — data, tools, prompts — implemented by Claude, ChatGPT, VS Code, Cursor and many others, so a server built once integrates everywhere. Adoption is its strongest argument. The cost vendor material omits is real: most clients load every tool definition up front, so descriptions occupy the window before any work starts, and every intermediate result round-trips through the model. Install servers casually and you pay that tax on every single turn.