MCP
The protocol that lets an agent call outside tools: one standard socket instead of a custom plug for every pair.
MCP stands for Model Context Protocol, the standard that lets an AI agent call outside tools. A tool server describes what it offers, and any agent that speaks the protocol can use it, with no custom code on either side. Before a standard like this, connecting every agent to every tool meant writing one integration per pair. Now each side implements the protocol once. When I say a capability ships as an MCP server, I mean it becomes a tool any of my agents can reach.
The detail worth holding onto is that the protocol’s shape decides where your problems show up. MCP servers come in two kinds: web services you reach over HTTP, and local programs that talk over standard input and output, which the spec calls stdio. The stdio kind has no network and no headers. So anything that needs to travel with a call, like who is actually asking, has to ride inside the message itself. That one design fact sits behind most of my gateway story, and it matters any time a middleman ends up between an agent and its tools.