MCP Registry

An MCP registry is a directory of Model Context Protocol servers — the place you go to find out what servers exist, what they do, and how to install or connect to them. Without registries, MCP discovery is word of mouth and GitHub searches; with them, thousands of servers become browsable, searchable metadata.

The term covers both the official registry run by the MCP project and the ecosystem of community indexes and marketplaces that consume its data.

The official registry lives at registry.modelcontextprotocol.io. Server authors publish a server.json manifest — name, description, repository, version, and the packages through which the server ships — and the registry validates it, verifies namespace ownership, and serves the result through a public API.

It is deliberately a metadata catalog, not an app store: it doesn't host code, rank servers, or process payments. Its job is to be the canonical, machine-readable source of truth that everything else can build on.

Downstream registries take the official catalog and layer on what it deliberately leaves out: categorization, search, usage signals, and commerce. Loomal's index imports servers from the official registry and adds x402 payment support, live-probed tool lists, and a claim flow — maintainers verify ownership of their GitHub repository to take control of their listing.

The monetization layer is the distinctive part: a claimed server can attach a per-call USDC price (minimum $0.01) so agents pay before each tool call runs, with settlement on Base. The official registry tells agents a server exists; an index like Loomal lets its author get paid for what it does.

Publishing once to the official registry is the highest-leverage move, since community indexes sync from it. The flow: write a server.json manifest, authenticate with the registry's publisher CLI, prove you control your namespace (via GitHub for io.github.* names), and publish. Updates are new manifest versions.

After that, check the downstream indexes that picked you up. On Loomal, claiming your imported listing lets you correct the description, surface the tool list, and set pricing if you choose to charge.

The words get used interchangeably, but there's a useful distinction: a registry catalogs servers; a marketplace adds a transaction layer — discovery plus the ability to buy and sell calls. Every marketplace contains a registry; not every registry is a marketplace. The official MCP Registry is firmly the former, by design.