Most people open Gemini, type the same background into a fresh chat for the tenth time, and wonder why AI feels like hard work. A Gem fixes that. It is a saved version of Gemini with one job, one set of rules and the documents it needs. Here is how I build one in about fifteen minutes, with a worked example you can copy.

Level: beginner to intermediate. You need a Google account and a computer. Gems are free in the Gemini app, so there is nothing to buy. If you use ChatGPT, my Custom GPT playbook covers the same idea there.

What a Gem is, and when it is worth building

A Gem is Gemini with its homework already done. You give it a name, write instructions once, optionally attach files, and from then on you open it like a tool rather than starting from nothing. You can create, edit and delete them only in the web app, which is why I do this on a laptop.

It is worth building a Gem when you do the same kind of task at least weekly and keep pasting in the same context: the tone you want for replies, the way you plan your week, the rules of a project. It is not worth it for one-off questions. Ask the one-off in a normal chat and move on.

The five steps

1. Pick one job, and write it as a sentence

The Gems that disappoint try to do everything. The ones I still use do exactly one thing. Finish this sentence before you touch the app:

This Gem takes [the thing I give it] and gives me back [the thing I want], in [the format I want].

My example: takes my rough list of tasks and appointments for the week and gives me back a realistic plan, one day at a time, with the three things that must happen first. If you cannot say it in one sentence, the Gem is too big. Split it.

2. Open Gemini and start a new Gem

On a computer, go to gemini.google.com, open Explore Gems in the side menu and choose New Gem. You will see a name box, an instructions box, a place to add files and a preview panel on the side. Name it for the job, such as "Week Planner", so you can find it in a list of ten later.

3. Write instructions with four parts

This is where the Gem is won or lost, and it uses the same four-part method as any good prompt: a role, the task, the background and the format. Here are the instructions behind my Week Planner:

You are a calm, practical planning assistant. I will give you a messy list of tasks, appointments and deadlines for the week. Build a day-by-day plan that fits them realistically. I work best in two focused blocks a day, with a gap at lunchtime, so never schedule more than five hours of focused work in one day. Start every plan with the three things that must happen first. If anything does not fit, say so and suggest what to move instead of squeezing it in. Use plain British English. Show the plan as a short list per day, no tables, no motivational talk. If I have not given you enough information, ask me one question before planning.

Notice the last line. A rule telling the Gem to ask rather than guess is the cheapest way to stop it inventing details. Write rules as things to do ("ask me one question") rather than a pile of things not to do, because clear positive instructions are easier for it to follow.

4. Add a knowledge file, but only if it earns its place

Under the knowledge section you can add files from your computer or Google Drive. Documents, PDFs, spreadsheets and text files are supported. This is useful when the Gem needs reference material it cannot guess, such as a style guide, your standard replies, a price list or a one-page summary of how you work.

For the Week Planner I attach a short note called "How I work": my usual commitments, my best hours and the things I never move. Keep files short and current. A fifty-page document of old notes gives the Gem more to get confused by, not less. And if a file has anything private in it, think before you upload it: the checklist for using AI at work safely is the filter I use.

5. Test it like a stranger, then save

Use the preview panel before you save, because it does not save the Gem on its own. Test three cases: a normal request, a request with too little information, and an awkward one that cannot fit, such as eight hours of tasks on a day with only three free. For each, ask: did it follow the format, did it ask when it should, did it say no when it should?

Fix the instructions where it slipped, test again, then save. Expect two or three rounds. The first draft of instructions is never the one you keep.

Three more Gems worth building

  • Reply Drafter. Instructions hold your tone and sign-off; you paste the email you received and a line on what you want to say. It drafts, you edit and send.
  • Meeting Prep. You paste an agenda or attendee list; it returns the three questions to ask and the one decision to leave with.
  • Recipe Rescuer. A knowledge file lists your dietary rules and what is in your cupboard; you give it three ingredients and it suggests dinner.

For work that needs your own documents at scale, a different tool may suit better. I compared the idea in Claude Projects, and Google's own assistant also lives inside your inbox, which I covered in Gemini in Gmail and Docs.

When a Gem goes wrong

  • It ignores a rule. Move that rule to the top of the instructions and make it a single short sentence. Long paragraphs bury rules.
  • It sounds generic. Add an example of the output you want, written by you, to the instructions or the knowledge file. Examples beat adjectives.
  • It makes things up. Add "If you are not sure, say so" and check any fact that matters. A Gem is still an AI, and it can still be wrong.
  • You lose it. Products change, so keep the instructions in a note of your own. I have seen reports that Google may fold Gems into a newer feature, and I couldn't confirm it from an official page. If it happens, a saved set of instructions means you rebuild in minutes.

Where to go next

One working Gem teaches you more than ten articles. Build the Week Planner this week, use it for a fortnight, then improve it. If you are newer to all this, Your First 30 Days With AI is my beginner course, and its first two modules are free. For other ways to put AI to work, see the AI tools hub.

Want more plain-English AI guides? I send one practical guide a week to my newsletter. Sign up here and I'll send the next one straight to your inbox.

Questions people actually ask

What is a Gemini Gem?

A Gem is a saved, reusable version of Gemini that you set up once with instructions and, if you like, reference files. Each time you open it, it already knows its job, so you stop retyping the same background into a new chat.

Are Gemini Gems free?

Google's help pages and several recent guides say Gems are available on the free Gemini plan, including adding files. Plans and limits change, so check the Gemini app itself for what your account allows.

Can I create a Gem on my phone?

Not at the time of writing. Creating, editing and deleting Gems is done in the Gemini web app on a computer; once a Gem exists you can usually use it from the mobile app too.

What is the difference between a Gem and a Custom GPT?

They do the same job in two ecosystems. A Gem lives in Google's Gemini and fits with Google Drive, Docs and Gmail; a Custom GPT lives in ChatGPT. The method of one clear job, firm instructions and a test set is identical.

Will my Gems stay available?

Probably, but products change. I have seen reports that Google may fold Gems into a newer feature, though I couldn't confirm it from an official page. Keep your instructions in a note of your own so you can recreate a Gem in minutes anywhere.

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