The MCP Registry gives MCP clients a list of MCP servers, and server.json is the standardized file that describes an MCP server for registry publishing, client discovery and package management. The registry launched in preview on 8 September 2025 and its API entered a v0.1 freeze on 24 October 2025. It is developed in the modelcontextprotocol/registry repository by a Registry Working Group; the latest release is v1.8.5 (26 October 2026). The MCP project is moving from MIT to Apache 2.0.
MCP Registry
The MCP Registry is the directory for Model Context Protocol servers — in the README’s words, “like an
app store for MCP servers.” Publishers describe a server in a server.json file; the registry validates and
lists it; and MCP clients query the registry API to find servers and the packages that run them.
- server.json - A generic format for describing an MCP server, specified with a JSON Schema, with the official registry layering extra requirements on top.
- Extension metadata - An optional
_metafield carries publisher metadata under reverse-DNS namespaces. - Preview, then freeze - Launched in preview on 8 September 2025; the Registry API entered a v0.1 freeze on 24 October 2025 so integrators could build against a stable surface.
- Open source service - The registry is a Go service backed by PostgreSQL, published as container images, with a live API and documentation.
- Working group - A Registry Working Group led by Radoslav Dimitrov (Stacklok) maintains it, with members from PulseMCP, TeamSpark and Ravenmail.
Where it sits. The registry is the discovery layer of the Model Context Protocol: the protocol says how a client talks to a server, mcp.json configures which servers a client uses, and server.json says where to find them. It solves for MCP what APIs.json and the AI Catalog aim at more broadly, and xRegistry already proxies it.
