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This guide shows how to integrate a pre-built MCP (Model-Capability-Plugin) server for Google Calendar so a local assistant (Claude Desktop in this example) can read and create events using your Google account. Follow these high-level steps:
  • Clone the MCP server repository
  • Enable the Google Calendar API and configure OAuth consent
  • Create OAuth credentials (Desktop app) and download the JSON
  • Point the MCP server at your credentials and run it
  • Add the MCP server to your Claude Desktop configuration
  • Interact with your Google Calendar from Claude

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1. Clone the repository

Open a terminal and clone the repo: 
git clone https://github.com/nspady/google-calendar-mcp.git
Example output on macOS: 
jeremy@MACSTUDIO mcpstuff % git clone https://github.com/nspady/google-calendar-mcp.git

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2. Enable the Google Calendar API and configure OAuth

  1. Open the Google Cloud Console — APIs Library: https://console.cloud.google.com/apis/library
  2. Search for and enable the Google Calendar API: https://developers.google.com/calendar
  3. After enabling the API, go to APIs & Services → Credentials to configure OAuth: https://console.cloud.google.com/apis/credentials
A screenshot of the Google Cloud Console "APIs & Services → Credentials" page showing API Keys and OAuth 2.0 client IDs. One Generative Language API key is listed, and the left sidebar and a code editor are visible in the background.
  1. Visit the OAuth consent screen: https://console.cloud.google.com/apis/credentials/consent
  2. Set an app name (for example, “MCP calendar tool”).
  3. Choose the user type:
    • Internal — restricts use to your organization.
    • External — allows any Google account to authorize the app (typical for local personal use).
  4. Provide contact info and save.
A browser window showing the Google Cloud Console "Project configuration" page with App Information and Audience options (Internal/External) selected. A dark-themed code editor/desktop is visible in the background.

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4. Create OAuth client credentials

  1. Create an OAuth 2.0 Client ID and choose Desktop app as the application type: https://developers.google.com/identity/protocols/oauth2
  2. Click Download JSON for the client credentials and save the file locally.
  3. Optionally rename the downloaded file to credentials.json (or another descriptive filename).

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5. Set the GOOGLE_OAUTH_CREDENTIALS environment variable and start the MCP server

Export an environment variable pointing to the absolute path of your credentials file, then start the MCP server. Example: 
export GOOGLE_OAUTH_CREDENTIALS="/Users/jeremy/demos/mcpstuff/google-calendar-mcp/credentials.json"
npm run start
When the server starts, it will open a browser window asking you to choose an account and authorize the app. If you see a “Google hasn’t verified this app” warning, that is expected for a local/test app. You can proceed after clicking the advanced option and continuing — only do this for apps you trust.
If you see the “Google hasn’t verified this app” page, proceed only if you trust the app and the credentials. Do not authorize unknown or public apps with your primary Google account.
A browser window showing Google's "Google hasn't verified this app" warning (red triangle icon and "Back to safety" button) overlaid on a code editor/IDE in the background.
After allowing access you should see confirmation in the console that authentication succeeded and tokens were saved locally. Typical console output: 
http://localhost:3500/oauth2callback?code=4/0AVMBsJiQmpdFfFIB1ArXnIZn8182nNKCBL72RB3A43btCF5c6ZP6Xg4mJtqWZeEE8xYkUw&scope=...
Authentication successful. Tokens saved to /Users/jeremy/.config/google-calendar-mcp/tokens.json

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6. Add the MCP server to Claude Desktop

Edit your Claude Desktop configuration file and add a new MCP server entry under mcpServers. The config file location depends on your OS:
OSConfig path
macOS~/Library/Application Support/Claude/claude_desktop_config.json
Windows%APPDATA%\Claude\claude_desktop_config.json
Example minimal JSON to add the Google Calendar MCP server: 
{
  "mcpServers": {
    "google-calendar": {
      "command": "npx",
      "args": ["@cocal/google-calendar-mcp"],
      "env": {
        "GOOGLE_OAUTH_CREDENTIALS": "/path/to/your/gcp-oauth.keys.json"
      }
    }
  }
}
A fuller example that includes multiple MCP servers: 
{
  "mcpServers": {
    "Meteo API": {
      "command": "/usr/local/bin/node",
      "args": ["/Users/jeremy/demos/Weather-MCP-Server/server.js"]
    },
    "Hacker News API 2": {
      "command": "/usr/local/bin/node",
      "args": ["/Users/jeremy/demos/mcpstuff/postman-mcp/postman-mcp-server/mcpServer.js"]
    },
    "google-calendar": {
      "command": "npx",
      "args": ["@cocal/google-calendar-mcp"],
      "env": {
        "GOOGLE_OAUTH_CREDENTIALS": "/Users/jeremy/demos/mcpstuff/google-calendar-mcp/credentials.json"
      }
    }
  }
}
After saving the config, restart Claude Desktop. Claude will detect the new MCP server and surface calendar-related tools.

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7. Interacting with the calendar from Claude

Once the MCP server is connected, use natural-language prompts like:
  • “What do I have on my calendar this week?”
  • “Create a new event on Saturday at 3 p.m. titled ‘Take a Walk’.”
Claude will display the MCP tool UI and request permission to use the calendar tool. You can grant permission temporarily (“Allow once”) or permanently (“Allow always”).
A computer desktop screenshot showing a code editor (file explorer on the left) and a dark pop-up window in the center displaying a "Weekly Calendar Overview" with listed events and times. The editor looks like Visual Studio Code with project files and a JSON file open.
Here is the permission modal that Claude shows before creating an event:
A screenshot of a code editor (likely VS Code) showing a project folder named "GOOGLE-CALENDAR-MCP" in the sidebar. In the center is a modal from "Claude" requesting permission to use a Google Calendar "create-event" tool with buttons for "Allow always," "Allow once," and "Decline."
After creating an event from Claude, verify it directly in Google Calendar:
A screenshot of Google Calendar in dark mode showing the week of July 20–26, 2025 with events like "Night of Fire," "Christi and AJ's wedding," and a highlighted "take a walk" event on Saturday, July 26 from 3–4 PM. The left sidebar with mini calendar and calendar list plus an event details pop-up are visible.

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Why use an MCP server?

MCP servers provide a consistent, tool-like interface that LLMs can call to perform API actions on your behalf. Benefits include:
  • Simplified authorization: OAuth flows and token storage are handled by the MCP server.
  • Structured responses: The MCP server returns parsed, predictable results for the assistant to consume.
  • Reusability: The same MCP server can be reused across multiple assistant deployments without re-implementing API logic.
This reduces the need to write custom API glue code every time you want the assistant to interact with an external service.
Keep your downloaded credential files and token files private. Do not commit credentials.json or tokens.json to a public repository.

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Closing

This walkthrough demonstrates how to run a Google Calendar MCP server locally, authorize it with Google OAuth, register it with Claude Desktop, and use natural language to read and create events. MCP servers let you expose APIs to LLM-based assistants cleanly while isolating authorization and API logic from the assistant itself.

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