Multilingual AI assistant: answering in French, Dutch and English from the same documents

Do you need to translate all your documents to have a multilingual assistant?

A single set of documents can be used to answer in French, Dutch and English, provided you check that the answers stay faithful in each language. Language models can read a document in French and then write an answer in Dutch or English. The knowledge base can therefore stay in the language it was written in.

For a Belgian organization, this avoids maintaining a full translation of every routine answer. The assistant looks for the information in the available document, then explains it in the visitor's language. This does not replace validating important terms, nor translating content that has to be published in a given language.

The right starting point is a reliable, clear and up-to-date document. A fluent translation of an ambiguous condition is still an ambiguous condition. Before working on languages, make sure your team understands and applies the same rule.

How does an AI assistant understand several languages?

Today's language models have been trained on texts in many languages. They can read a question in Dutch, understand a passage in French and write an answer in English in the same operation. This ability varies by language: it is very good for French, Dutch, English and German, weaker for languages that are less present in the training data.

In assistants that search passages by meaning, this search also works across languages. The system turns each passage into a representation of its meaning, called an embedding. With a multilingual embedding model, a Dutch question about the "opzegtermijn" can find a French passage about the "délai de préavis", because their meanings are close. This is semantic search, and it makes a knowledge base in a single language possible.

This mechanism has two practical limits. A very specialized term or an in-house abbreviation can be poorly matched with its equivalent in the other language. And the model translates the general meaning with ease but may choose an everyday word where your sector uses a precise term. Both are solved with tests and an in-house glossary, described below.

Which content should you still translate?

Prepare in each language the content visible before the conversation and validate the terms whose approximate translation could change the meaning.

• What the visitor sees before writing: the greeting, the suggested questions and the useful starting information must exist in the languages offered
• Trade terms: a legal, technical or administrative term deserves an approved wording and a clear context in the document
• The proper names of your offers: the name of a plan or service should be kept as it is, unless an official version exists

Terms such as "EPC" and "PEB", or "onroerende voorheffing" and "précompte immobilier" (property tax), deserve to be placed side by side in your documents, without assuming that all the related procedures are identical. Specify the context that applies to your business.

Also keep conditions and caveats in translation examples. A phrase like "subject to availability" must not disappear because the answer sounds more natural without it.

Documents that still need translating for legal reasons

The assistant does not replace the documents you must provide in a given language. Belgium's Code of Economic Law, for example, requires certain information intended for consumers to be written at least in the language of the language region where the product or service is offered. Your terms and conditions, instructions and contractual documents follow their own rules. The assistant can explain them in another language, but the reference document remains the one you officially publish.

If in doubt, have your adviser check which documents must exist in which language. Then load the reference version into the assistant, and state in its instructions that it should point to the version published in the visitor's language when one exists.

How do you write an in-house glossary for languages?

An in-house glossary is a short document that fixes the translation of your important terms. It serves the team as much as the assistant. It often fits on one page and has three columns:

Add a fourth column if a term must never be translated (the name of an offer, a district, a public service). Load this glossary into the knowledge base and mention it in the assistant's prompt: "use the glossary's equivalents for the terms it lists".

Belgian usage to anticipate

Belgian French and Belgian Dutch have their own words, which models do not always choose spontaneously. A Belgian visitor writes "septante" and "nonante", talks about their "GSM", their "kot" if they are a student, their "syndic" if they own a flat. On the Dutch side, people write "kmo" rather than "mkb", "btw-nummer", "gemeentehuis". The assistant understands these words without difficulty; it uses them less naturally in its answers.

If your audience is local, ask in the prompt for Belgian usage: "write numbers the Belgian way", "use Belgian administrative vocabulary". Then check during testing that answers do not mix usages, for example by citing a procedure from the Netherlands where a Belgian one is expected.

Register and form of address

Choose a register and keep it in every language. In French, "vous" remains the norm in an SME's customer relations. In Dutch, "u" is common in Belgium for a first contact, while "je" appears in more informal sectors. In English the question does not arise in the same way, but the tone can range from very formal to relaxed. Note this choice in the prompt, with an example greeting per language.

How does the assistant choose the language of its answer?

The assistant starts from the language requested by the page or the browser, then follows the one the visitor writes in. A customer who opens the conversation in French and continues in Dutch can therefore receive the rest in Dutch. A preference clearly expressed by the visitor should guide the exchange.

Plan for messages that mix languages, foreign product names and very short replies. If the choice remains ambiguous, asking for clarification is better than a guess based on the contact's name or address.

On the team's side, the person who takes over the conversation reads the history as it was written. Do not confuse the assistant's ability to answer with the availability of a colleague who can continue in that language. This distinction must be built into how the service is organized.

Edge cases to plan for

Some situations come up often enough to deserve a written rule:

• A one-word message: "Price?" or "Openingsuren" is enough to determine the language, but "OK" or an order number is not. The assistant should keep the previous language
• A bilingual message: a Brussels visitor may start in French and slip in a Dutch term. The dominant language of the sentence guides the answer
• A language not offered: a visitor writes in German, Spanish or Arabic. Decide whether the assistant still answers in that language, mentioning that the team can only take over in French, Dutch or English, or whether it politely offers to continue in one of the service's languages
• A change of language mid-conversation: the assistant follows the visitor, but the context already given must be kept

How do you avoid contradictions between languages?

Avoid contradictions by designating a reference version for each piece of information and removing outdated versions. Do not let different conditions coexist without stating which situation each one applies to.

If the visiting policy changes in French, check any Dutch and English guides that still contain the old instruction. Correct the documents at the source, then repeat the relevant tests. Simply asking the assistant to "translate properly" does not fix a contradiction in the documents.

Language errors can also become made-up answers: the assistant completes an uncertain expression with a plausible condition. Ask it to keep caveats, cite the document and flag missing information rather than freely adapting your commitments.

One reference language or several?

Two set-ups are possible. The first keeps a single reference language, often the one the team works in, and lets the assistant explain in the other languages. It is the simplest to maintain: one update, one source. The second keeps complete documents in each language, because they already exist for the website or for legal reasons.

In the second case, the main risk is drift: the French version is updated, the Dutch one is not. The assistant may then find two different answers depending on the language of the question. If you keep several versions, name a person responsible for keeping them in sync and date each document. When in doubt, remove from the base the version that is no longer maintained.

Which languages should a Belgian SME offer?

Offer the languages your visitors actually use and for which you can organize a consistent service. Belgium has three official languages: French, Dutch and German. The Brussels-Capital Region is officially bilingual in French and Dutch. English may be useful to your customers without being an official Belgian language.

To decide, look at the requests received, the languages of the documents and the team's ability to take over. An assistant offered in French, Dutch and English therefore does not cover all the country's official languages. If your audience asks for German, address that need explicitly when choosing the solution.

Also avoid inferring every customer's preferences from where the business is located. A Brussels SME may welcome visitors with very varied language habits.

What languages change in the visitor's journey

The choice of language is not limited to the conversation. Check the consistency of the whole journey:

• The page the visitor comes from: if your website exists in Dutch, the assistant should open in Dutch on those pages
• The greeting and suggestions: they are the first words read, so write and review them in each language rather than translating them on the fly
• The links cited in answers: a Dutch-speaking visitor prefers to be sent to the Dutch page when it exists
• The handover confirmation: "the team will reply within one working day" must be accurate in each language, including the language of the reply
• The follow-up e-mail: if it is sent automatically, it must go out in the language of the conversation

Which tests should you run before launch?

Test the same situations in the languages offered, then compare the meaning of the answers and the sources used. Have important wording reviewed by someone competent in the language concerned.

A useful test looks for errors that change a decision: an omitted fee, an assumed availability or a misunderstood procedure. Grammatical correctness matters, but it is not enough to validate the service.

A three-pass testing method

For a first launch, a simple method gives good results:

1. Write twenty real questions in the language of your documents, with the expected answer and the passage that supports it
2. Have a native speaker of each other language rewrite them in their own words rather than translating literally; that is how your visitors will ask them
3. Compare the three answers to each question: same information, same caveat, same source. Note every gap, even if it seems minor

Keep this list. It is used again with every significant change to the documents or the instructions, and it grows with the questions that caused problems in production.

What does multilingual support bring in concrete Belgian situations?

Multilingual support helps make the same information accessible to visitors who would not express it in the document's language. The following situations are fictitious examples of Belgian SMEs, not customer cases.

A property manager in Brussels has a maintenance guide written in French. A tenant asks in Dutch how to report an incident. The assistant explains the procedure and cites the guide. For an individual dispute, it hands over to the team. Uses in property management call for this separation between general procedure and personal file.

In a coliving house in Ghent, an English-speaking applicant asks about the arrival rules. The answer can draw on the French guide, but it must keep the conditions about reception and key handover. An exceptional permission must be confirmed by a person. Coliving is in fact one of the sectors where English weighs most, with international residents.

A shop in Namur can, in the same way, explain its returns procedure to a Dutch-speaking customer. The translation must not change the purchase conditions or invent an exchange option.

One assistant per language or one for all?

Some tools require one assistant per language, each with its own documents and settings. Others allow a single assistant that answers in several languages from the same base. For an SME, the second approach is almost always preferable: one prompt to maintain, one base to update, one history for the team.

Several assistants make sense when the audiences are truly different, not just their languages. A coliving house may have one assistant for applicants, which talks about prices and availability, and another for residents, which talks about house rules and maintenance. Each then answers in the three languages. The split follows the role, not the language.

The case of German

German is an official language in Belgium, spoken mainly in the German-speaking Community, in the east of the province of Liège. A business serving that region, or visitors from Germany, Luxembourg or Austria, may benefit from adding it. Language models answer well in German; the question is rather about the human handover and the official documents that must exist in that language. If the team does not speak German, say so clearly in the greeting rather than suggesting a full service.

How much does multilingual support cost?

With a document-based assistant, the language of the answer changes little in the usage cost: the model writes in Dutch as quickly as in French. The real cost lies elsewhere. You need to write and review the greeting and suggestions in each language, build the glossary, test the same questions several times and organize the human handover. Count this time at the start, then with every significant change to your terms.

Be wary of plans that bill each language as an add-on. For a Belgian SME, Dutch and French are not an extension but the core of the market; English often follows closely in sectors that welcome expatriates or students. The cost of an AI assistant should therefore be compared on the basis of the languages you really need.

How do you measure language use after launch?

After a few weeks, look at the breakdown of conversations by language. It confirms or corrects your starting assumptions: a Walloon business may find a larger share of Dutch-speaking visitors than expected, a Brussels business a large share of English.

Above all, look at the questions left unanswered, language by language. If there are more of them in one language, the cause is often a poorly matched term or a document that only exists in another language with different vocabulary. Complete the glossary, add a sentence of context to the document, then run the test again. The resolution rate per language is a good indicator to track these corrections.

How do you organize the human handover in another language?

Organize the handover by stating who can handle the request, in which language and during which hours. Human handover must keep the history and the open question so the visitor does not have to start again.

If no one is available in the requested language, explain the real options and collect a useful way to get in touch. Do not promise a call-back in a language the team does not speak. A language preference kept for future exchanges falls under a memory that has been explained to and accepted by the contact.

A practical solution is to note in the request passed on the language of the conversation and a short summary in the team's language. The colleague then sees at a glance what it is about and can decide who calls back. Our article on when an assistant should hand over details what a handover should contain.

Common mistakes with a multilingual assistant

• Machine-translating every document before loading it: translation errors become sources that the assistant cites with confidence
• Keeping versions that are out of sync: two languages, two conditions, two different answers to the same question
• Forgetting the greeting: a hastily translated greeting gives a poor first impression, whatever the quality of the answers
• Promising a handover in every language when the team only speaks French
• Testing a single language and assuming the others will follow
• Ignoring Belgian usage: an answer that says "mkb" to a Flemish visitor or "soixante-dix" to someone from Brussels feels like it comes from somewhere else
• Letting the assistant translate offer names: "Formule Sérénité" becomes "Serenity Plan" in an answer, and the visitor cannot find the offer on the website

Most of these mistakes can be fixed in an hour, provided they are spotted. Hence the value of regularly reading a few conversations in each language, not only in the team's. Someone who reads Dutch without speaking it fluently will already catch most gaps in meaning on terms or prices.

Where do you start to offer multilingual support?

Start with a one-hour audit of the requests, the documents and the languages your team can support. Then choose the situations to test before extending the service.

KernChat, developed by KERN-IT in Brussels, answers in French, Dutch and English from the organization's documents, with a greeting and suggested questions written for each language, and a workspace available in those languages. Its set-up method helps prepare the sources, the tests and the handover to the team.