Extension Structure

The typical folder structure of a newly created extension looks like this:

my-extension/
├── manifest.json
├── package.json
├── tsconfig.json
├── index.ts
├── components/
│   └── my-widget.tsx
└── tests/

Sources

The entry point is index.ts (at the root). It initializes the MCP server, registers all widgets, and starts the stdio transport. Each widget resides in a separate file within the components/ folder and is imported by index.ts.

Support files

manifest.json is the extension manifest. It defines the name, version, author, and server launch details. See the field reference below for a full list.
package.json is a standard npm package file. It must include a build script, which is used by the eney-skills-cli dev command. See package.json below for more details.
tsconfig.json configures TypeScript for ESM output, which is required by the MCP runtime. Most likely, you won't need to edit this file.
tests/ is a folder containing basic boilerplate tests to help you get started with testing your extension.

manifest.json

Provides the essential metadata Eney and the MCP runtime need to identify and run your extension.

{
  "manifest_version": "0.3",
  "name": "my-extension",
  "version": "1.0.0",
  "description": "What this extension does",
  "author": {
    "name": "Your Name"
  },
  "server": {
    "type": "node",
    "entry_point": "index.js",
    "mcp_config": {
      "command": "node",
      "args": ["${__dirname}/index.js"],
      "env": {}
    }
  },
  "license": "MIT"
}

Field	Description
`name`	Unique extension identifier (use kebab-case)
`version`	Semantic version string
`description`	Short description shown in Eney
`author.name`	Extension author name
`server.entry_point`	Entry point file (typically `index.js`)
`server.mcp_config.command`	Command used to launch the server
`server.mcp_config.args`	Arguments passed to the launch command. Use `${__dirname}` as a placeholder for the extension folder path; Eney resolves this at runtime
`server.mcp_config.env`	Environment variables injected into the server process

package.json

Standard npm package file. It manages your extension's dependencies and includes the build script required to compile TypeScript into JavaScript.

{
  "name": "my-extension",
  "version": "1.0.0",
  "type": "module",
  "scripts": {
    "build": "tsc"
  },
  "dependencies": {
    "@eney/api": "latest",
    "@modelcontextprotocol/sdk": "latest"
  },
  "devDependencies": {
    "typescript": "^5"
  }
}

The script must be named exactly "build". The CLI calls npm run build when running eney-skills-cli dev.

tsconfig.json

Configured for ESM output, which is required by the MCP runtime.

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "outDir": ".",
    "strict": true,
    "jsx": "react-jsx",
    "jsxImportSource": "@eney/api"
  },
  "include": ["**/*.ts", "**/*.tsx"],
  "exclude": ["node_modules"]
}

Because the module system is ESM, all local imports must use .js extensions even when the source file is .ts. For example: import { runScript } from "./helpers/run-script.js".

index.ts

The entry point for your extension. Initializes the MCP server, registers widgets, and starts the stdio transport.

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { setupUIXForMCP } from "@eney/api";
import MyWidget from "./components/my-widget.js";

const server = new McpServer(
  { name: "my-extension", version: "1.0.0" },
  { capabilities: { logging: {}, resources: {} } },
);

const uixServer = setupUIXForMCP(server);

uixServer.registerWidget(MyWidget);

async function main() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
}

main().catch(console.error);

To register multiple widgets, import each one and call uixServer.registerWidget() for each.

components/

Contains React widget components. Each file exports a widget created with defineWidget. Use .tsx for components with JSX. See the Widgets reference for all available UI primitives.