> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tai42.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# The marketplace

> The plugin index: listings, items, versions, and advisories.

The marketplace is the ecosystem's plugin index. A running server browses it,
installs a plugin from it in one command, and hears from it when a published
version turns out to be bad.

## A metadata index

The registry stores metadata, never packages. A **listing** points at the
plugin's real distribution channel — its pip package and its source
repository — and installing resolves that pointer and installs by source: a
GitHub-sourced release is downloaded and its SHA-256 verified against the
digest the registry recorded at ingest, while a PyPI-sourced release pins the
exact version and relies on PyPI's file immutability. The registry's catalog is
curated: it lists the ecosystem's
first-party plugins, and every listing carries an `official` trust tier.

## Listings and items

One installable plugin carries many capabilities: a single package can ship
tools, extensions, and agents together. The registry indexes each contained
capability as its own **item** row with a kind, categories, and tags — because
an item is what you search for. You search at item level and install at plugin
level: finding the `generate_uuid` tool leads you to install the listing that
carries it.

## Versions

Each listing publishes **versions**. A version records the exact release, its
artifact, and the [tai42-contract](/concepts/layering) compatibility range it
declares, so a server can tell whether a release fits its contract before
installing. The registry validates every release's artifact against its
listing before publishing it — a release that fails validation is never
served.

## Advisories and the kill switch

An **advisory** flags affected versions of a listing with a severity and a
summary. Separately, a version can be **killed** — a registry-side kill switch
that refuses to resolve that version at all, so it can never be installed. The
two are distinct: an advisory is a published warning that can later be
withdrawn, while a killed version is pinned out of resolution.

See [Advisories](/marketplace/advisories) for how a server checks.

## The plugin descriptor: tai-plugin.yml

Every plugin describes itself with a `tai-plugin.yml` — the plugin descriptor —
at its repository root and inside its built wheel. It names the listing, the
package, the version, the contract range, and the `provides` list of every
item the plugin carries.

The registry indexes a plugin from this file and validates the artifact against
it; the installer uses the `provides` list to patch the server
[manifest](/concepts/manifest) per provided item. It is a different file from the
server manifest: `tai-plugin.yml` describes what a plugin *offers*, the server
manifest declares what a server *loads*.

See [The plugin descriptor](/guides/authors/plugin-descriptor) to author one.

## Installing into a server

Install is a server-side operation: the server resolves the listing, installs
the verified package into its own environment, patches its manifest per
provided item, and reloads. The server records the marketplace ref and installed
version locally, so `installed`, update checks, and advisories answer from
local truth. The whole flow is one CLI command or one Studio click — see
[Install a plugin](/marketplace/install).

## See also

* [Browse and search](/marketplace/browse) — find plugins and items.
* [Install a plugin](/marketplace/install) — install, update, uninstall.
* [The manifest](/concepts/manifest) — the server-side file the installer patches.
* [Ecosystem catalog](/reference/catalog) — the packaged offline catalog.