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Glossary
Agents and protocols

stdio transport

The way a local MCP server talks to its client: over the standard input and output of a process the client starts.

With stdio, the client launches the server as a child process on the same machine and exchanges messages through its input and output streams. There is no port and no network address, so nothing else on the network can reach it.

That is also why authentication rarely applies: the only party that can talk to the server is the program that started it. What the server can do is limited only by the permissions of the account it runs as.

Why it matters

It settles which risks apply. A stdio server cannot be reached from the network, and it runs with your privileges on your machine.

The mistake everyone makes

Reading local as safe. A stdio server cannot be attacked over the network, and it can read every file your account can.

Related terms

Streamable HTTP
The MCP transport for servers reached over the network, where the client sends each message to an HTTP endpoint.
MCP server
A program that exposes tools and data to a model through the Model Context Protocol.
Least privilege
Granting the narrowest access that makes the job possible, and nothing beyond it.
Remote MCP server
An MCP server hosted by somebody else and reached over the network, rather than installed and run on your machine.
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