CLI / Terminal.

The terminal is a text-based way to control your computer by typing commands instead of clicking around. It's the screen you see hackers using in movies, the raw backend straight into your machine. A CLI (command-line interface) is any tool you drive that way.

Here's why it matters for agents. Your agent lives in the terminal too, so any tool that has a CLI is instantly usable by your agent. No special integration needed, it just runs the commands.

That's also why I often reach for a CLI over an MCP (Model Context Protocol) now. An MCP is the standard way to plug a tool into an agent, but it's heavier. If your agent runs in the terminal, a CLI beats an MCP every time. They're lean and fast, and they don't eat your Context window the way a stack of MCPs does.