---
title: "Client extensions"
description: "Client extensions let a particular client define additional manifest data, files, and behavior. Agent Plugins reserves no central registry; namespaces use reverse-domain identifiers to avoid collisions."
canonical: https://agentpluginsdirectory.com/spec/plugin-authors/client-extensions
last-updated: 2026-09-21
---

# Client extensions

Client extensions let a particular client define additional manifest data, files, and behavior. Agent Plugins reserves no central registry; namespaces use reverse-domain identifiers to avoid collisions.

## Manifest data
Put client-specific data under `extensions` in `plugin.json`:

```json title="plugin.json"
{
  "$schema": "https://agent-plugins.org/schemas/1.0.0/plugin.schema.json",
  "name": "example-plugin",
  "extensions": {
    "com.example.client": {
      "setting": true
    }
  }
}
```

Each extension value is an object. A client ignores namespaces it does not implement without validating their contents.

## Extension directories
Client-owned files live in a top-level directory whose name exactly matches the namespace:

```text
example-plugin/
├── plugin.json
├── skills/
└── com.example.client/
    └── hooks/
        └── hooks.json
```

A client can use manifest data, an extension directory, or both. The namespace owner defines their contents, validation, relationships, and failure behavior.

Client extensions are not portable Agent Plugins components. Other clients can ignore them without affecting conformance.