Glossary · Phase 9 · Model Context Protocol

Dual-era

Also written: dual-era server, dual-era client

MCP software that speaks both the old handshake and the new stateless style, answering each caller in whichever it opens with.

Try it now

The practice server is dual-era. Send server/discover and read the versions, capabilities and instructions it returns. An unsupported version gets a 400 listing the supported ones, and the legacy initialize still works. The headers are covered in the Streamable HTTP lesson.

Learn it properly

Discovery, capabilities and the two eras · server/discover, declared capabilities, and talking to legacy and modern software alike. About 30 minutes.

Create a free account See what's in the lesson

Never trained an AI?

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

Teach it to write