How I built AI add-ins for Microsoft 365 and Google Workspace (10 apps, free to start)

Hey IH 👋

I've been building CoreGPT Apps — a suite of AI add-ins that bring GPT directly inside the productivity tools people already use every day.

The problem I kept seeing:

Most people who want AI help with their work end up doing this:

1. Write something in Word/Docs/Outlook

2. Copy it

3. Switch to ChatGPT in the browser

4. Paste it

5. Copy the result back

6. Switch back

It's friction that adds up fast. And it breaks your focus constantly.

What I built:

CoreGPT integrates GPT directly into the apps where the work actually happens — no tab switching, no copy-pasting.

Right now there are 10 integrations:

• Microsoft 365: Word, Excel, PowerPoint, Outlook, OneNote, Teams

• Google Workspace: Docs, Sheets, Slides, Forms

Each one is purpose-built for that app. For example:

• In Outlook — draft replies, rewrite tone, summarize long threads

• In Excel — generate formulas from plain English descriptions

• In Word — write, rewrite, summarize, translate, and change tone in-place

• In Teams — summarize meeting transcripts, draft follow-ups

Free tools as a top-of-funnel:

Alongside the add-ins, I built 18 free web tools (word counter, AI email subject generator, grammar checker, JSON to table, etc.) to drive organic traffic and let people try the AI quality before installing anything.

Where things are at:

• Live on both the Microsoft AppSource and Google Workspace Marketplace

• Free tier available — no credit card required to start

• Working on SEO content and improving conversion from the free tools

What I'm figuring out now:

• Which acquisition channel works best for B2B productivity tools like this (organic vs. marketplace rankings vs. content)

• Pricing — currently free-to-start, thinking about where to draw the line

Happy to answer questions about building Office/Google add-ins, the marketplace approval process, or the tech stack. It was a surprisingly painful road.

👉 coregptapps.com