A comprehensive Google Apps Script solution that integrates CustomGPT with Google Workspace, providing:

Google Chat Bot - Interactive chatbot for Google Chat
Web App - Standalone chat interface with Material Design
Google Sheets Integration - Use CustomGPT from spreadsheets
Gmail Add-on - AI responses in Gmail

Get you CustomGPT.ai RAG API key here, needed to use this integration.

More information on GitHub - https://github.com/Poll-The-People/customgpt-integrations

Features

Google Chat Bot

Slash commands (/help, /info, /starters, /reset)
Interactive card responses with buttons
Conversation context within spaces
Rate limiting per user
Welcome messages and onboarding

Web App Interface

Material Design UI with light/dark themes
Real-time chat interface
Starter questions
Citation support
Export chat history
Mobile responsive

Security & Performance

API key security with Script Properties
Rate limiting (10/min per user, 100/hour)
Response caching (5 minutes)
Domain-based access control
Error handling and recovery

Setup Instructions

1. Create Google Apps Script Project

Go to script.google.com
Click New Project
Name your project (e.g., "CustomGPT Integration")

2. Add Project Files

Copy these files to your project:

Code.gs - Main server-side code
index.html - Web app interface
styles.html - CSS styles
javascript.html - Client-side JavaScript
appsscript.json - Project manifest

3. Configure Script Properties

In Apps Script editor, go to Project Settings (gear icon)
Scroll to Script Properties
Add these properties:
- CUSTOMGPT_API_KEY - Your CustomGPT API key
- CUSTOMGPT_AGENT_ID - Your agent/project ID
- ALLOWED_DOMAINS - (Optional) Comma-separated list of allowed domains

4. Deploy as Web App

Click Deploy > New Deployment
Choose type: Web app
Settings:
- Description: "CustomGPT Chat Interface"
- Execute as: User accessing the web app
- Who has access: Choose based on your needs:
  - Anyone - Public access
  - Anyone with Google account - Requires login
  - Only myself - Private use
  - Anyone within [your domain] - Organization only
Click Deploy
Copy the Web App URL

5. Set Up Google Chat Bot

Usage Guide

Google Chat Bot Commands

Direct Message: Just type your question
/help - Show available commands
/info - Display agent information
/starters - Show starter questions
/reset - Reset conversation context

Web App Features

Chat Interface:
- Type questions in the input field
- Press Enter to send (Shift+Enter for new line)
- View responses with citations
UI Controls:
- Theme toggle (light/dark)
- Agent information
- Reset conversation
- Export chat history
Starter Questions:
- Click any suggested question to ask it
- Customize in agent settings

Google Sheets Integration

Add this custom function to use in sheets:

/**
 * Query CustomGPT from Google Sheets
 * @param {string} question The question to ask
 * @return {string} The response from CustomGPT
 * @customfunction
 */
function CUSTOMGPT(question) {
  if (!question) return "Please provide a question";
  
  try {
    const response = sendToCustomGPT(question, "sheets");
    return response.content;
  } catch (error) {
    return "Error: " + error.message;
  }
}

Usage in Sheets:

=CUSTOMGPT("What is the weather forecast?")
=CUSTOMGPT(A1)  // Reference a cell

Gmail Add-on

To create a Gmail add-on:

Add to appsscript.json:

{
  "gmail": {
    "name": "CustomGPT Assistant",
    "logoUrl": "https://www.customgpt.ai/logo.png",
    "contextualTriggers": [{
      "unconditional": {},
      "onTriggerFunction": "onGmailMessage"
    }]
  }
}

Add handler function:

function onGmailMessage(e) {
  // Create card with CustomGPT integration
  return buildGmailCard(e);
}

Advanced Configuration

Rate Limiting

Adjust in CONFIG object:

RATE_LIMIT_PER_USER: 10,     // Per minute
RATE_LIMIT_PER_HOUR: 100,    // Per hour
CACHE_DURATION: 300,         // 5 minutes

Domain Restrictions

Set ALLOWED_DOMAINS in Script Properties:

example.com,anotherdomain.com

Enable checking:

REQUIRE_DOMAIN_CHECK: true

Custom Styling

Modify styles.html to customize:

Colors and themes
Fonts and sizes
Layout and spacing
Animations

API Response Handling

Customize response processing:

// Add to sendToCustomGPT function
if (response.someField) {
  // Custom logic
}

Deployment Options

1. Personal Use

Deploy as "Only myself"
No authentication needed
Full access to your data

2. Team/Organization

Deploy to your Google Workspace
Set domain restrictions
Manage permissions via Google Groups

3. Public Service

Deploy as "Anyone"
Implement additional security
Monitor usage and costs

Monitoring & Logs

View Logs

In Apps Script editor, click Executions (📊)
Filter by function or status
Click any execution for details

Stackdriver Logging

Logs are automatically sent to Google Cloud Logging:

View in Cloud Console
Set up alerts
Export to BigQuery

Usage Tracking

Add custom tracking:

function trackUsage(action, user) {
  console.log(`Usage: ${action} by ${user}`);
  // Send to analytics service
}

Troubleshooting

Bot Not Responding

Check API key and agent ID in Script Properties
Verify Chat API is enabled
Check execution logs for errors

Rate Limit Errors

Increase limits in CONFIG
Implement user notifications
Consider caching strategies

Authentication Issues

Check OAuth scopes in manifest
Verify deployment settings
Test with different access levels

Performance Issues

Enable caching
Optimize API calls
Use batch operations

Best Practices

Security:
- Never hardcode API keys
- Use Script Properties
- Implement domain checks
- Monitor access logs
Performance:
- Cache frequent responses
- Batch API calls
- Minimize external requests
- Use async operations
User Experience:
- Provide clear error messages
- Show loading states
- Offer helpful suggestions
- Maintain conversation context
Maintenance:
- Regular testing
- Monitor quotas
- Update documentation
- Version control

API Reference

Core Functions

// Send message to CustomGPT
sendToCustomGPT(message, conversationId)

// Check rate limits
checkRateLimit(userEmail)

// Get agent information
getAgentInfo()

// Get starter questions  
getStarterQuestions()

Web App Functions

// Send message from web UI
sendWebMessage(message)

// Get configuration
getWebConfig()

// Export functions
exportChat()

Chat Bot Handlers

// Main webhook handler
doPost(e)

// Message handler
handleChatMessage(message)

// Command handler
handleCommand(command, message)

Extending the Integration

Add Custom Commands

case '/custom':
  return handleCustomCommand(parts, message);

Integrate with Other Services

function integrateWithService(data) {
  const serviceUrl = 'https://api.example.com';
  return UrlFetchApp.fetch(serviceUrl, {
    method: 'post',
    payload: JSON.stringify(data)
  });
}

Create Scheduled Tasks

function scheduledTask() {
  // Run daily summaries, reports, etc.
}

Set up time-based trigger in Apps Script.

Support & Resources

CustomGPT Links

Platform Documentation

License

MIT License - Feel free to modify and distribute.