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Most chatbots are built to finish your task. That suits an email, not a problem you must later solve alone in the exam hall. Custom instructions change that default once, so every study chat starts with a tutor instead of an answer machine.
What happens when students use AI help without rules?
In a field experiment published in PNAS in 2025, researchers studied nearly 1,000 maths students in grades 9 to 11 at a large high school in Turkey (Bastani et al., PNAS). Some practised with GPT-4 and some had no AI. One AI group used a plain ChatGPT-style interface. The other used a "GPT Tutor". Its prompts included teachers' solutions, common student mistakes and an instruction to give hints without giving away the answer (full text on PubMed Central).
While students had the AI, practice grades rose 48% with the plain version and 127% with the tutor version. Once access was taken away, the plain-version group scored 17% lower than students who never had it. The tutor version's safeguards largely removed that harm. The authors' explanation is that, without guardrails, students used GPT-4 as a "crutch".
You won't have teacher-written solutions, but you can copy the core idea: who you are, how to help, and what never to do. For the wider evidence, read what tutoring research says about hints versus answers.
Where do you put custom instructions in ChatGPT, Gemini and Claude?
ChatGPT: on the web, open Settings, then Personalization, and type into the Custom instructions field. On phones it sits under Settings, then Customize ChatGPT (OpenAI Help Center).
Gemini: make a Gem. Click Explore Gems, then New Gem, name it and write its instructions. Google suggests covering persona, task, context and format (Google Gemini Help). You must be 13 or over, or the applicable age in your country, to create and use Gems with a personal account (Google Gemini Help).
Claude: account-wide instructions live in Settings and apply to all your conversations. A project can carry its own instructions, and free accounts can create up to five projects (Claude Help Center).
Account-wide instructions affect every chat, so a separate Gem or project for study keeps the tutor rules where you want them.
What should tutor-style instructions include?
Good instructions have five parts:
Who you are: class, board, target exam.
Where you struggle: the chapters or question types that trip you up.
A hint ladder: how help should step up, one small hint at a time.
A no-full-answers rule, with one clear exception.
A check at the end: explain it back, then try a similar problem.
Sample custom instructions you can copy
This sample is written for a Class 12 student preparing for JEE Main. Swap in your own details and paste the lines into the box.
About me: I am in Class 12 (CBSE), preparing for JEE Main. I am fairly strong in mechanics and weak in electrostatics and organic reaction mechanisms.
Your role: act as a patient tutor. Your goal is that I can solve problems alone in the exam, not that this problem gets solved.
Hint style: when I share a problem, first ask what I have tried. Then give one hint at a time, smallest first: which concept applies, then the first step, then where my working went wrong. Wait for my reply after each hint.
Rules: never give the final answer or a full worked solution unless I type SHOW SOLUTION after at least two attempts of my own. Do not write graded homework or assignments for me. If you are unsure of a fact or a result, say so.
Checks: when I get it right, ask me to explain in two sentences why the method works, then give me one similar problem with different numbers.
Style: short replies, SI units, simple English. Use Hindi if I ask.
For revision days, add a quiz mode using these rules and example prompts for making a chatbot quiz you.
How do you check the instructions are working?
Start a new chat, paste a problem you have already solved, then type "just tell me the answer". A well set-up chatbot should offer a hint instead. If it gives in, move the no-answers rule to the top and shorten it.
Next, check the hints themselves. Chatbots still make errors in calculations, so test any final number it confirms with this five-step way to check AI maths.
When are custom instructions not enough?
Instructions are a patch on a tool built to answer. They do not tell the chatbot what you already know, and in long chats it may not stick to every rule, so test again now and then. Fermi's AI tutor is built to teach rather than answer: it works out what you already know, builds a plan for the session and checks understanding as it goes, so you start with a tutor without writing the rules yourself.
Whichever tool you use, set it up tonight and test it with one solved problem.
