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Build your own AI assistant for your team

Your own AI assistant is an AI chat with fixed instructions and your own files in it: a custom GPT in ChatGPT, a Project in Claude or an agent in Microsoft Copilot. Your team builds it itself, without code, and the first version is up and running in an afternoon. Below are the step-by-step plan, three examples to copy, the pitfalls and when you're better off having something built.

  • By Olaf Lemmens
  • Updated 27 October 2026
  • No code

An afternoon of building

Afternoon
  1. 13:00Choose a goalOne task: drafting quotes for the inside sales team.
  2. 13:30Write the instructionsRole, tone, what it does and doesn't do.
  3. 14:15Add filesPrice list, three good quotes, the terms and conditions.
  4. 15:00Test with real requestsTen requests from last week, without names.
  5. 16:00Share with the teamWith one owner who keeps it up to date.

What is your own AI assistant?

Your own AI assistant is an AI chat that knows your work. You give it fixed instructions and your own files once, and after that nobody has to paste them again. In ChatGPT that's called a custom GPT, in Claude a Project and in Microsoft Copilot an agent. You build it without code.

Think of a new colleague who, on their first day, has read the price list, the style guide and ten good quotes, and has a note on their desk with the house rules. You don't have to explain how things work every time. You ask your question, and it answers in your tone, with your facts.

The difference from plain prompting: with a prompt you give all the context again every time. With an assistant, that context is already in it. That saves time, and more importantly: the whole team works with the same instructions and the same files. Fatima's quote then looks like Mark's.

In the APO method this is build layer 2: assistants and projects. Just like prompting, build layer 1, your team does this itself. It's also the second phase of AI adoption, after prompting and before workflows and agents.

An assistant is a good prompt you no longer have to type. Plus the files you no longer have to paste.

How is it different from an AI agent or workflow?

An assistant waits until you ask something and only works in the conversation. A workflow starts by itself, for example on an incoming email, and carries out fixed steps in your systems. An agent gets a goal and chooses the steps itself. Your team builds an assistant itself; workflows and agents you have built.

Side by side:

  • Assistant. You start the conversation. It reads, writes and thinks along, but does nothing in your ERP or CRM. You copy the result to where it needs to go.
  • Workflow. Starts on an event: an email, a form, every morning at eight. Pulls data from one system, lets AI do the work and puts the result in the other. A human checks where it matters.
  • Agent. Gets a goal instead of a route, chooses which systems to consult and puts the result to a human.

Watch the words. In Microsoft Copilot, your own assistant is called an agent. In our classification it stays an assistant as long as you start the conversation and it does nothing in your systems. More about the difference in what is an AI agent?, and what agents do in practice on AI agents.

Custom GPT, Claude Project or Copilot: which one do you choose?

Choose the tool your team already uses, with a business account. An assistant in a tool nobody ever logs into won't get used. If everyone works in ChatGPT, make a custom GPT. If your team works in Claude, make a Project. If your organization lives in Microsoft 365, look at an agent in Copilot.

At heart they do the same thing: you give it a name, instructions and files, and you share the result with colleagues. The differences are in the details, and those change every few months.

  • ChatGPT: custom GPT. An assistant with its own instructions and files, which you can share with colleagues.
  • Claude: Project. A workspace with fixed instructions and documents, in which you have your conversations. With skills you can also teach Claude a fixed way of working, such as how you structure a quote.
  • Microsoft Copilot: agent. An assistant within Microsoft 365. Handy if the files it needs are already in SharePoint or OneDrive.

Whether you can create and share an assistant, and with whom, depends on your subscription and on what your administrator has switched on. Check that before you start. And don't use a personal account: what you put in an assistant is company knowledge.

How do you build your own AI assistant? In five steps

Choose one clear goal, write the instructions, add only the files it really needs, test with ten real examples and share it with an owner who keeps it up to date. The first version is up and running in an afternoon. It gets good in the weeks after that, by using it and refining it.

1. Choose one goal

One assistant, one task. 'Drafting a quote for the inside sales team' is a good goal. 'Everything for sales' isn't. The narrower the goal, the better the answers, and the easier it is to see whether it works well. Choose a task that comes back every week, and for which someone currently has to give the same explanation over and over.

2. Write the instructions

The instructions are the fixed prompt that goes along with every question. Use the same building blocks as for a good prompt: role, context, task, example and format. Also write down what it does not do, and what it does when it doesn't know. A setup to copy:

You are the quote assistant of [company]. You help the inside sales team draft a quote from a customer request. Only use the prices from 'Price list 2026' and follow the structure of the sample quotes. Never make up prices, discounts or delivery times. If something isn't in the files, put TO CONFIRM in the text. First ask about what's missing from the request. Write in a formal, businesslike and brief style.

3. Add knowledge files

Only what it really needs. For a quote assistant: the current price list, a few good quotes as examples and the general terms and conditions. Not the whole 'Sales' folder. More files doesn't mean better answers: old versions and half-finished drafts actually cause mistakes. Give the files clear names with a date, so you can see which version is in there. And put nothing in it that not everyone with access is allowed to see.

4. Test with real examples

Take ten requests, emails or questions from the past few weeks, remove the names and let the assistant handle them. Put the result next to what you made yourselves. Where does it go wrong? Adjust the instructions and test again. Also test the edge cases: a request for something you don't sell, a question whose answer isn't in the files. Does it then honestly say it doesn't know? Great.

5. Share it and appoint an owner

Share the assistant with the team, with a short explanation: what is it for, what isn't it for, and who is the owner? That owner keeps the files up to date, collects feedback and adjusts the instructions. Put it in the calendar: fifteen minutes every month to check that everything is still correct.

Where do your own assistants go wrong?

Almost always on one of these three: too much in one assistant, outdated files and no owner. You don't see them in the first week, but you do after three months, when nobody uses it anymore.

Too much in one assistant

The 'sales assistant' that writes quotes, makes LinkedIn posts, answers customer questions and does the weekly schedule as well. The instructions turn into a wall of text full of contradictions, and it does everything a little. Better to make three small assistants that each do one thing well.

Outdated files

Last year's price list is still in there. So is the new one. The assistant picks one, or mixes them. An assistant is as good as its files. Agree on this: whoever changes the price list also updates the assistant.

No owner

Someone made it enthusiastically in a workshop, shared it with the team and went back to business as usual. Six months later nobody knows which version is in it. Without an owner, every assistant dies a quiet death.

And three smaller ones

  • Not tested. In the demo it looks good, but with the first real request it makes up a discount.
  • Too many assistants. Twenty assistants that look alike, and nobody knows which one is right. Keep a list with the goal and the owner of each assistant, just like the AI register from your AI policy.
  • Sensitive files. Anyone allowed to use the assistant can in principle ask anything that's in the files. So put nothing in it that not everyone with access is allowed to see.

When are you better off having it built?

As soon as the work no longer fits in the chat. Do you keep retyping the assistant's result by hand into another system, does the work come by dozens of times a day, or is the knowledge too large or restricted per user? Then an assistant is no longer enough, and you need a workflow, an agent or a RAG application.

Five signals:

  • You copy between systems. The request comes in by email, you paste it into the assistant and retype the quote into the CRM. A workflow does that in one go, and you check.
  • The volume is high. Ten quotes a week work fine through an assistant. Two hundred customer emails a day don't.
  • It has to start by itself. An assistant waits for you. If the work has to begin as soon as the email comes in, you need a workflow.
  • The knowledge is large or sensitive. Hundreds of documents, or permissions that differ per employee. Read what is RAG?
  • You want to measure and look back. What went in, what came out, who approved it? With an assistant in the chat, you have little grip on that.

In the APO method those are build layer 3, workflows with n8n, and build layer 4, custom work such as agents and RAG. We build those, within the AI Partnership, from € 4,500 per month, excluding VAT. What agents do in practice is on AI agents.

A good assistant is never wasted work. The instructions, examples and test cases you made for it are exactly what's needed to build a workflow or agent later. Want to teach your team to build assistants themselves first? We do that in a workshop on your own work.

Three examples

Three assistants to copy

Each example with the goal, the files, the key instruction and what to watch out for. Copy them and fill them in with your own work.

  • Inside sales

    Quote assistant

    Goal: from a request in the inbox to a draft quote.

    Files: the current price list, three good quotes and the general terms and conditions.

    Key instruction: never make up prices or discounts, and put TO CONFIRM next to anything that's missing.

    Watch out: update the price list in the assistant as soon as it changes.

  • Marketing and communications

    House style writer

    Goal: rewriting texts in your tone, from newsletter to job ad.

    Files: the style guide, five texts you're proud of and a list of words you do and don't use.

    Key instruction: don't change the content, only the tone, and flag facts you can't check.

    Watch out: give examples, not adjectives. 'Warm and professional' tells it nothing.

  • Customer service

    Customer question assistant

    Goal: a draft answer to a customer question, which the employee checks and sends.

    Files: the returns policy, the delivery terms and the twenty most frequent questions, with the right answer.

    Key instruction: answer only from the files and say where it's written. If you don't know, say so.

    Watch out: paste customer emails without names, or only in a business account with agreements.

In one table

Build it yourself or have it built?

Your team makes an assistant itself. A workflow or agent, we build. This is how you see what fits your question.

Your own assistantWorkflowCustom agent or RAG
Build layer in the APO method2: your team makes it3: NinA builds, with n8n4: NinA builds, custom work
What sets it offYou, with a questionAn email, form or fixed timeAn event or an instruction
Works in your systems·✓✓
KnowledgeFiles you add yourselfData from your systemsLots of documents and systems, with permissions per user
Role of the humanReads, copies and checksChecks where it mattersApproves before anything happens
CostsYour business licenseWithin the AI Partnership, from € 4,500 per monthWithin the AI Partnership, from € 4,500 per month
Fits whenYou keep pasting the same contextThe same work comes up dozens of times a weekThe work has lots of exceptions or the knowledge is large

Swipe sideways to see all columns →

All amounts excluding VAT. The partnership starts with the € 6,000 AI Quick Scan. Exactly what an assistant can do in your tool varies by subscription.

Questions

Frequently asked questions about your own AI assistant

What is your own AI assistant?

An AI chat with fixed instructions and your own files, so it knows your work without you explaining everything every time. In ChatGPT that's called a custom GPT, in Claude a Project and in Microsoft Copilot an agent. Your team builds it itself, without code. The assistant helps in the conversation, but does nothing in your systems.

How do you build a custom GPT or Claude Project?

In five steps. Choose one clear goal, write instructions with a role, context, task, example and format, add only the files that are needed, test with ten real examples without names and share it with the team, with one owner who keeps it up to date. The buttons differ per tool; the approach is the same everywhere.

What's the difference between an AI assistant and an AI agent?

An assistant waits until you ask something and only works in the conversation: you copy the result to your systems. An agent gets a goal, chooses the steps itself and works in your systems, such as the ERP or CRM, with a human who approves. Your team builds an assistant itself; an agent you have built. Note: in Microsoft Copilot, your own assistant is also called an agent.

Which files do you put in an AI assistant?

Only what it needs for its task: the current version of the price list, the policy or the style guide, plus a few examples of good work. No old versions and no half-finished drafts, because they cause mistakes. And no data that not everyone with access to the assistant is allowed to see.

Is your own AI assistant safe for company data?

That depends on your account and your agreements. Use a business account with a data processing agreement, where the provider doesn't use your data for training. Don't put personal data in the files unless your policy allows it, and keep in mind that anyone allowed to use the assistant can in principle ask anything that's in it.

How many assistants does a team need?

As few as possible, as many as needed. Start with one assistant for the task that comes up most often. If that works, make the next one. One assistant per task works better than one assistant for everything. Keep a list with the goal and the owner of each assistant, so they don't multiply out of control.

When is your own assistant not enough?

When you keep retyping the result by hand into another system, when the work comes by dozens of times a day, when it has to start by itself on an email or form, or when the knowledge is too large or too sensitive for a few files. Then you need a workflow, an agent or a RAG application. NinA builds those within the AI Partnership.

Can NinA teach my team to build assistants?

Yes. In a half-day workshop at your location, your team works with its own tool and its own examples, and everyone goes home with an assistant for a task that comes back every week. A workshop costs € 4,500, excluding VAT. Within the AI Partnership, training comes out of the package hours. More on AI training.

Build assistants yourselves, or have them built?

Book a fifteen-minute intro call. We look at your team's work and tell you honestly what you can do yourselves and where building pays off.

  1. 01

    Intro call

    Fifteen minutes, no strings. Where does work get stuck and what do you want to achieve?

  2. 02

    AI Quick Scan

    One day on site. Within a week, a business case and a roadmap.

  3. 03

    AI Partnership

    A dedicated team that builds, trains and shows what it delivers every month.

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