Build Your Own AI Assistant Without Coding: Step by Step

Do you type the same explanation into a chatbot every Monday: who you are, what your business does and what tone you write in? Building your own AI assistant solves that, and you do not need to programme anything. In this article, you will learn how to build a Gem in Gemini, a project in Claude or a project in ChatGPT step by step, with examples for your work and your own business. You will also learn what to watch out for with privacy, and why you are better off not building a new GPT any more.

What exactly is a custom AI assistant?

A custom AI assistant is a chatbot that you give fixed instructions and background knowledge once, so it uses them in every conversation. That means you do not have to explain what you want again and again.

Think of it like a new colleague. On day one, you explain how you work, what tone you use in emails and where the price list is. After that, that colleague can get on with things. With an AI assistant, you write that explanation down once.

Alongside instructions, you can often add files too, such as a product overview, a style guide or a list of frequently asked questions. That is called your assistant’s knowledge. Not sure yet how to write a good prompt for AI? Then first read what a prompt is and how to get more out of it. Writing instructions works in exactly the same way, only you save them.

Gem, Claude project or ChatGPT project: what is the difference?

All three basically do the same thing: they store instructions and knowledge, so you get a custom chatbot. The biggest difference is how you use them, what they cost and how you share them.

Note for ChatGPT. According to OpenAI’s help page about GPTs, personal accounts (Free, Go, Plus and Pro) can no longer create or publish new GPTs. And the FAQ about retiring GPTs says that OpenAI wants to phase out custom GPTs entirely, planned for 11 December 2026. That is why we recommend a project in ChatGPT.

What	Gem (Gemini)	Project (Claude)	Project (ChatGPT)
Free to create?	Yes, even with the free version	Yes, but with more limits than on a paid plan	Yes, but with fewer files per project than on a paid plan
Where do you create it?	On a computer via the website, then also usable in the app	On claude.ai	On chatgpt.com or in the app
Fixed instructions	Yes	Yes, as project instructions	Yes, as project instructions
Add your own files	Yes	Yes, as project knowledge	Yes
Useful for	Recurring tasks, such as rewriting emails or text	A fixed job or client with lots of documents	Anyone who already uses ChatGPT every day

Prices, limits and features change often. So always check the current price and terms with the provider before you subscribe.

How can you build your own AI assistant in five steps?

You build a custom AI assistant by first defining the goal, then writing instructions, adding knowledge, testing and fine-tuning. That order works in every tool.

1. Choose a task. Start small, with a job you do every week. For example: checking quotes, writing LinkedIn posts or answering customer emails.
2. Write the instructions. Describe the role (you are my editor), the audience, the tone and the desired result. Also say what the assistant must not do, such as making up prices.
3. Add knowledge. Upload only files that are really needed, such as a sample text or a list of frequently asked questions. Remove personal data first.
4. Test with tricky questions. Ask questions whose answer is not in your files. A good assistant will then say it does not know. You can even put that directly in your instructions.
5. Improve and save. Is something not right? Change the instructions and test again. After a few rounds, you will often have an assistant that does what you want.

A little-known tip: let the AI interview you first. Ask the chatbot to ask you five questions about your task, then write the instructions together. That usually gives you better instructions than filling in an empty box yourself. Further down in this article, you will find a ready-made prompt for this.

How to build a Gem in Gemini

You create a Gem on a computer via gemini.google.com and then you can also use it in the app on your phone. All you need is a Google account.

1. Open Gemini in your browser and sign in with your Google account.
2. In the menu, go to Gems and choose to create a new Gem. The position of the buttons sometimes changes, so check the settings too if you cannot see it straight away.
3. Give your Gem a clear name, such as Quote check or Mail help.
4. Write your instructions. Not sure what to write? Then click the magic wand: Gemini will help you expand the instructions.
5. If you want, add files as knowledge.
6. Test the Gem in the preview window and save it.

In its tips for Gems, Google recommends starting with a ready-made Gem, such as Brainstormer or Career guide. Does one already look almost like what you need? Make a copy and adapt the instructions. That saves work if you do not want to start from scratch.

How to create a project in Claude

A project in Claude is a dedicated workspace with fixed instructions, your own files and its own conversation history. Ideal if you need the same background again and again for a client or job.

1. Go to claude.ai and sign in.
2. Click Projects in the menu on the left and create a new project.
3. Give the project a name and a short description, for example Client Bakery De Vries.
4. Fill in the project instructions: who you are, what Claude should do and what tone to use.
5. Upload the documents Claude should know, such as a brief or previous texts.
6. Start a conversation within the project. Claude will then automatically use your instructions and files.

According to Anthropic’s explanation of projects, a project can also handle lots of documents: if your project is almost full, Claude will automatically look up the relevant pieces. Note: separate conversations within a project do not know about each other, unless you add the information to the project knowledge. Sharing projects with colleagues is possible on business plans (Team and Enterprise).

Can you still create a custom GPT in ChatGPT?

Not with a personal account any more, and it is not wise to start one now either. OpenAI plans to phase out custom GPTs; the planned date is 11 December 2026. After that, GPTs and their pages will no longer be accessible.

Do you use ChatGPT in a business workspace (Business, Enterprise or Edu)? Then until now you could still create GPTs if the administrator allowed it. But OpenAI plans to stop creating new GPTs there soon as well. As a successor, OpenAI points to plugins: bundles with fixed instructions, files and linked apps. Which options you get depends on your subscription and workspace. Already have a GPT? Follow the message in your account about moving it over.

For most readers, a project in ChatGPT is the easiest route. Free users can also create projects, although they can add fewer files. This is how it works:

1. Sign in to chatgpt.com and choose a new project in the menu on the left.
2. Give the project a clear name, such as Customer emails.
3. Open the project settings and paste in your fixed instructions.
4. Add the files ChatGPT should know.
5. From now on, start your conversations within this project so ChatGPT uses your instructions and files.

If you are new to this chatbot, first read how to get started with ChatGPT in ten minutes.

Which AI assistant can you build for your work or business?

The best AI assistant takes over a task you do often and that is usually much the same every time. Here are five examples you can build today.

• Mail helper for customer questions. Upload your frequently asked questions and delivery terms. The assistant drafts a reply in your tone, which you check and send. Want to go further? Then read about AI customer service for freelancers and SMEs.
• Quote checker. Add your standard prices and terms. Paste in a draft quote and ask whether anything is missing.
• Social media writer. Add three posts that performed well. The assistant writes new posts in the same style.
• Meeting summariser. Paste in your own notes and let it turn them into a short report with action points. Do not use names or sensitive details.
• B1-level language coach. Let the assistant rewrite your texts in simple language, useful for newsletters or information for customers.

A custom assistant is not real automation that carries out tasks by itself. You still have to guide it manually. But you do save time, because you do not have to explain what you want again and again.

What should you watch out for with privacy in a custom AI assistant?

Never put personal data from customers, applicants or colleagues into your assistant, unless your organisation has made clear arrangements about this. Everything you upload ends up on the provider’s servers.

That this is not just theory is shown by a warning from the Dutch Data Protection Authority. According to Financieele Dagblad, the regulator received dozens of reports of data breaches in 2025 because staff put sensitive information into AI chatbots. At the municipality of Eindhoven, CVs and documents about youth care ended up in free versions of chatbots, among other things.

• Remove data. Replace names, addresses and customer numbers with made-up examples before you upload anything.
• Check your settings. In ChatGPT, Gemini and Claude, you can choose in the settings whether your conversations may be used to improve the AI. Turn that off if you do not want that.
• Ask about the policy at work. Many employers have rules about which AI tools you may use. A business subscription often gives better arrangements for your data.
• Check the answers. Even an assistant with your files can make things up. Read everything through before sending it to a customer.

If you work with personal data, the rules of the GDPR, the European privacy law, still apply. If you are not sure whether something is allowed, check with your privacy officer or a lawyer.

Try it yourself: let the AI write your instructions

With the prompt below, you let the chatbot interview you first. After that, you get instructions you can paste straight into your Gem or project. Fill in the parts in square brackets yourself.

Frequently asked questions

Can I build a custom AI assistant for free?

Yes. In Gemini, you can create a Gem with the free version, and Claude and ChatGPT also offer projects to free users, with more limits. Always check the current terms and price with the provider.

Why can I no longer create a GPT in ChatGPT?

OpenAI has switched off the creation of new GPTs for personal accounts, including paying Plus and Pro users. OpenAI also plans to phase out custom GPTs entirely, planned for 11 December 2026, and points to plugins as the successor. A project in ChatGPT is a good alternative for most people.

Do I need to be able to code to build an AI assistant?

No. You write the instructions in plain language and upload files in just a few clicks. If you can write a clear email, you can also set up an AI assistant.

Is my information safe in a Gem or project?

Your files are stored on the provider’s servers. So do not put personal data or confidential documents in there, and check in the settings whether your conversations may be used to train the AI.

Which tool is best for a custom AI assistant?

For most beginners, a Gem in Gemini is an easy start, because it can be free and takes few steps. If you work with lots of documents per job or client, a project in Claude is a good fit. If you already use ChatGPT every day, choose a project in ChatGPT.

If you want to understand better how these chatbots actually work first, read our plain-English explanation of what AI is. Then choose a task you still do this week and build your first assistant in fifteen minutes.