MCP
The protocol that lets an agent call outside tools: one standard socket instead of a custom plug for every pair.
MCP, the Model Context Protocol, is the standard that lets an AI agent call external tools. A tool server describes what it offers, any agent that speaks the protocol can use it, and neither side needs custom code for the other. Without a standard, connecting every agent to every tool means one integration per pair; with it, 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.
It earns a definition because the protocol’s shape decides where problems live. MCP servers come in two kinds: web services reached 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 must travel with a call, like the identity of whoever is asking, has to ride inside the message itself. That one design fact is behind most of the gateway story, and it is worth holding onto whenever a middleman sits between an agent and its tools.