What it does
Lets you "install" your own expert into Gemini for a task you keep repeating: you set the role and instructions once, and stop re-explaining the context in every chat. You can attach up to 10 knowledge files (PDFs, documents, spreadsheets, including from Google Drive) — the Gem will answer strictly from them.
How to set it up
- gemini.google.com → on the left, Explore Gems → New Gem.
- Name the Gem and write its instructions. Google suggests the RTCFE skeleton (Role · Task · Context · Format · Example); or write the goal in one sentence and hit the "magic wand" — Gemini expands it into full instructions for you.
- Under Knowledge → Add files, upload your documents (from your device or from Drive).
- Test it with a prompt on the right → Save. Available on both free and paid plans.
When to use it
- ✅ The same task keeps coming back: a brand-guidelines assistant, a spec reviewer, a support helper backed by your knowledge base.
- ✅ You need answers grounded strictly in your documents, not in the internet average.
- ❌ A one-off question — a normal chat is simpler; for a ready-made mode, use the premade Gems.
Example
You create a Gem called "Editor for our tone of voice": instructions plus a file with the brand book. From then on you paste any text into it and it edits strictly by your style rules.