opentabs-plugin-google-calendar

OpenTabs plugin for Google Calendar

Project Structure

google-calendar/
├── package.json          # Plugin metadata (name, opentabs field, dependencies)
├── icon.svg              # Optional custom icon (square SVG, max 8KB)
├── icon-inactive.svg     # Optional manual inactive icon override
├── src/
│   ├── index.ts          # Plugin class (extends OpenTabsPlugin)
│   └── tools/            # One file per tool (using defineTool)
│       └── example.ts
└── dist/                 # Build output (generated)
    ├── adapter.iife.js   # Bundled adapter injected into matching tabs
    └── tools.json        # Tool schemas for MCP registration

Configuration

Plugin metadata is defined in package.json under the opentabs field:

{
  "name": "opentabs-plugin-google-calendar",
  "main": "dist/adapter.iife.js",
  "opentabs": {
    "displayName": "Google Calendar",
    "description": "OpenTabs plugin for Google Calendar",
    "urlPatterns": ["*://*.calendar.google.com/*"]
  }
}

• main — entry point for the bundled adapter IIFE
• opentabs.displayName — human-readable name shown in the side panel
• opentabs.description — short description of what the plugin does
• opentabs.urlPatterns — Chrome match patterns for tabs where the adapter is injected

Custom Icons

By default, the side panel shows a colored letter avatar for your plugin. To use a custom icon, place an icon.svg file in the plugin root (next to package.json):

google-calendar/
├── package.json
├── icon.svg              ← custom icon (optional)
├── icon-inactive.svg     ← manual inactive override (optional, requires icon.svg)
├── src/
│   └── ...

How it works:

• opentabs-plugin build reads icon.svg, validates it, auto-generates a grayscale inactive variant, and embeds both in dist/tools.json
• To override the auto-generated inactive icon, provide icon-inactive.svg (must use only grayscale colors)
• If no icon.svg is provided, the letter avatar is used automatically

Icon requirements:

• Square SVG with a viewBox attribute (e.g., viewBox="0 0 32 32")
• Maximum 8 KB file size
• No embedded <image>, <script>, or event handler attributes (onclick, etc.)
• Manual icon-inactive.svg must use only achromatic (grayscale) colors

Development

npm install
npm run build       # tsc && opentabs-plugin build
npm run dev         # watch mode (tsc --watch + opentabs-plugin build --watch)
npm run type-check  # tsc --noEmit
npm run lint        # biome

Adding Tools

Create a new file in src/tools/ using defineTool:

import { z } from 'zod';
import { defineTool } from '@opentabs-dev/plugin-sdk';

export const myTool = defineTool({
  name: 'my_tool',
  displayName: 'My Tool',
  description: 'What this tool does',
  icon: 'wrench',
  input: z.object({ /* ... */ }),
  output: z.object({ /* ... */ }),
  handle: async (params) => {
    // Tool implementation runs in the browser tab context
    return { /* ... */ };
  },
});

Then register it in src/index.ts by adding it to the tools array.

Authentication

Plugin tools run in the browser tab context, so they can read auth tokens directly from the page. The SDK provides utilities for the most common patterns:

import { getLocalStorage, getCookie, getPageGlobal } from '@opentabs-dev/plugin-sdk';

// localStorage — most common
const token = getLocalStorage('token');

// Cookies — session tokens, JWTs
const session = getCookie('session_id');

// Page globals — SPA boot data (e.g., window.__APP_STATE__)
const appState = getPageGlobal('__APP_STATE__');

Iframe fallback: Some apps (e.g., Discord) delete window.localStorage after boot. getLocalStorage automatically tries a hidden same-origin iframe fallback before returning null, so you don't need to handle this case manually.

SPA hydration: Auth tokens may not be available immediately on page load. Implement polling in isReady() to wait until the app has hydrated before your tools run. See the comments in src/index.ts for an example polling pattern.

Shared Schemas

When 3 or more tools share the same input or output shape, extract common Zod schemas into a shared file to avoid duplication:

// src/schemas/channel.ts
import { z } from 'zod';

export const channelSchema = z.object({
  id: z.string().describe('Channel ID'),
  name: z.string().describe('Channel name'),
});

export type Channel = z.infer<typeof channelSchema>;

Then import and reuse in your tools:

// src/tools/list-channels.ts
import { channelSchema } from '../schemas/channel.js';

export const listChannels = defineTool({
  name: 'list_channels',
  displayName: 'List Channels',
  description: 'List all available channels',
  icon: 'list',
  input: z.object({}),
  output: z.object({ channels: z.array(channelSchema) }),
  handle: async () => {
    // ...
    return { channels: [] };
  },
});

This keeps your tool schemas DRY and makes it easy to evolve shared types in one place.