The Extensions Framework
An extension is a capability neither side has to support: named with a mandatory vendor prefix, declared fresh in the metadata of every request, and safe to ignore, so the core protocol never has to grow to fit one vendor's idea. Identify a well formed extension identifier by its mandatory vendor prefix, and name a real official one and a real third party one. Explain where a client declares extension support and where a server declares its own, and why both live in per-request meta rather than a one time handshake. Compute the active extension set for a request from what the client asks for and what the server actually supports. Apply graceful degradation: fall back to core behavior for an optional extension, and reject a request that needs a mandatory one the two sides never mutually activated. Trace an extension's lifecycle from an Extensions Track SEP through an experimental repository to an official identifier, and state what forces a new identifier. MCP's core specification has to stay something every implementation can fully support, the same guarantee that lets any client discover and drive any server it has never seen before. Real deployments want things the core was never going to standardize for everyone: a tool that renders an interactive chart instead of a wall of text, a way to…
The Extensions Framework: An extension is a capability neither side has to support: named with a mandatory vendor prefix, declared fresh in the metadata of…
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