The **open‑rpc/specification-extension-spec** repository provides a formal JSON‑Schema for “Specification Extensions” (prefixed with `x-`) that let developers augment the OpenRPC schema with custom, non‑standard features. It ships the meta‑schema and example extensions as an npm package (`@open‑rpc/specification-extension-spec`) for use in tooling and for prototyping new OpenRPC capabilities before they become part of the core specification, targeting OpenRPC tool creators and API designers who need extendable, machine‑readable contract definitions.