An AI agent is an AI system that can take actions on its own, not only produce text in reply to a prompt. Give it a goal and access to tools, and it decides which tool to call, in what order, without a person clicking each step.
The agent is the part that decides what to do; a connection such as MCP only declares what is possible and carries out the request. In Birta's case, the agent is whichever tool already holds your finished site, Claude Code, Cursor, or a chat, deciding when to publish it.
For how an agent uses a connection like MCP to act, see what MCP is and why it matters for publishing.