How does one agent talk to another agent? And how does an agent discover new tools at runtime, rather than having them hardcoded at startup?

Two protocols are shaping how agents interact with the outside world: MCP (Model Context Protocol) for connecting agents to tools and data, and A2A (Agent-to-Agent) for connecting agents to each other. They solve different problems and work together.

Understanding both, and knowing when to use which, is essential for building agent systems that scale beyond a single process on your laptop.