Glossary · Phase 9 · Model Context Protocol

Stdio

Also written: standard input, standard output, stdin, stdout, stderr

A program's standard streams: input it reads, output it writes, and a separate stream for errors and logs. Local MCP servers talk over them.

Try it now

Three streams, one rule: nothing but protocol on stdout.

Transports I: stdio · Newline-delimited JSON over a subprocess's standard streams. About 30 minutes.

Teach a small one to write, right in your browser. It takes about 20 seconds and needs no account.