How to Write a Good Prompt for Your WhatsApp Sales Assistant

A prompt is the instruction you give the AI so it knows how to respond on your WhatsApp. If you want to automate WhatsApp messages without them sounding robotic, that's the key: the clearer and more specific your prompt, the better the suggestions your team will receive. Saying "reply to messages" is not the same as giving detailed instructions about your business, your tone, and what to do in each situation. In this article we show you how to write prompts that work.

What is a prompt and why does it matter?

A prompt is basically an instruction you give the AI. It can be a question, a set of rules, or a description of what you expect it to do. In the context of a WhatsApp sales assistant, your prompt is what tells the AI how to behave, what information to use, how to talk to your customers, and when to escalate to a human.

The difference between a vague prompt and a well-crafted one is huge. A vague prompt generates generic, confusing responses that don't represent your brand. A clear, specific prompt makes the AI understand your business, your tone, and your goals, and makes the response suggestions genuinely useful.

The key elements of a good prompt

• Business context: what you sell, to whom, and what problems you solve
• Tone and personality: how you want the AI to speak on behalf of your brand
• Relevant information: data about products, prices, policies, hours
• Limits and restrictions: what it should NOT do, when to escalate to a human
• Clear objectives: what you want to achieve in each conversation (sell, inform, retain)

Step by step: how to structure your prompt

1. 1Introduce your business in one or two sentences. Example: 'We are an online store for women's sportswear. We sell local and international brands with shipping nationwide.'
2. 2Define the tone. Formal or friendly? Fun or serious? Example: 'Speak in a warm, close, and friendly tone. Use emojis occasionally. Avoid jargon that a new customer wouldn't understand.'
3. 3List your key information: main products, prices (if possible), business hours, return policies, payment methods.
4. 4Explain your objectives. Example: 'The goal is to help the customer find what they're looking for, answer questions about products, and make the purchase easier. If the customer wants to make a return, offer to transfer them to an agent.'
5. 5Define when to escalate. Example: 'If the customer is angry, asks to speak with a human, or asks a question you can't answer with the information you have, offer to transfer them to a sales agent.'
6. 6Add concrete examples. If you can, show how you want it to respond in typical situations. AI learns best from examples.

Common mistakes when writing prompts

• Being too vague: 'Respond like a salesperson' doesn't give enough information. Be specific.
• Forgetting context: the AI doesn't know what you sell if you don't tell it. Include details.
• Not defining limits: if you don't tell it what NOT to do, it can make mistakes. Be clear about restrictions.
• Prompts that are too long and confusing: the AI processes clear, organized instructions better. Use bullet points and structure.
• Not updating the prompt: if something changed in your business (new product, hours, policy), update the prompt. Otherwise, the AI will keep using old information.
• Ignoring tone: if your brand is fun but you give it a formal prompt, the AI will sound out of place.

Example of a well-made prompt

Here's an example you can adapt to your business:

"You are the sales assistant for Café Artesano, a small coffee shop in Palermo that sells specialty coffee and homemade desserts. Your tone is warm, friendly and approachable. Respond in Spanish, without being too formal. You can use emojis occasionally (☕, 🍰). Our main products are: Espresso Coffee ($150), Americano Coffee ($120), Medialunas ($80), Chocolate Cake ($250). We're open Monday to Friday 8-18hs, Saturdays 9-17hs, closed Sundays. We deliver in the Palermo area (within 2km) free of charge. If the customer asks about deliveries to another area, offer to coordinate and charge for shipping. If someone asks for something we don't have, suggest alternatives. If the customer is angry or asks to speak to a manager, offer to transfer to a human. Don't make up information about products or prices you're not sure about."

How to improve your prompt over time

A prompt isn't something you write once and you're done. It's a living document that needs to be reviewed and improved.

• Review the responses the AI generates. Is there anything you don't like? Adjust the prompt.
• Pay attention to the questions you receive frequently. If there's something the AI can't answer well, add information to the prompt.
• Ask your team for feedback. If human agents see the AI saying something strange, it's a sign the prompt needs adjustments.
• Test small changes. Don't change everything at once; make gradual adjustments and observe the results.
• Update information regularly. If you launch a new product, change schedules or policies, update the prompt.

Practical tips for writing better

• Use clear, direct language. Avoid unnecessary jargon or confusing phrases.
• Be specific with numbers. Instead of 'affordable prices', state the exact prices.
• Include examples of conversations. Show how you want it to respond in real cases.
• Organize the information into sections. This way the AI processes it better and it's easier to update later.
• Think about the customer. What do they need to know? What matters to them? That has to be in the prompt.
• Be honest about limits. If the AI can't do something, it's better to say so than to let it make things up.

Writing a good prompt is a skill that improves with practice. Don't expect it to be perfect the first time. What matters is to start with something clear and specific, observe how it works, and adjust as needed. With a well-made prompt, your AI assistant will be much more useful for your business and your customers will have a better experience on WhatsApp.

Second-order questions: what happens after you write your prompt

Once your prompt is ready, questions arise that you didn't think of at the beginning. For example: what happens if the customer writes in another language? What if they ask for something that isn't in your product list? How do you handle a conversation that goes off on tangents?

The short answer is: the prompt doesn't solve everything. That's why serious tools combine the prompt with business rules and human supervision. In Wando, for example, the AI suggests responses and your team approves them with one click. That gives you control without having to program every scenario.

Another common question is whether the prompt replaces a human agent. Not entirely: the AI speeds up responses and handles simple queries, but delicate situations (angry customers, complaints, complex questions) need a person. Your prompt should make it clear when to escalate, and your team has to be prepared to take over those conversations.

Finally, think about evolution. Your prompt today won't work next year. Products change, schedules change, your brand tone evolves. Reviewing it regularly is not optional, it's part of maintaining your assistant.

• Define what happens with messages in other languages or outside business hours.
• Establish a clear process for escalating conversations to humans.
• Schedule regular prompt reviews, don't leave it static.

Concrete example: from a vague prompt to an effective one

Let's look at a real case. An aesthetics business writes: "Reply to WhatsApp messages in a friendly way and offer appointments." That prompt is so generic that the AI doesn't know what services you offer, how much you charge, or what coverage areas you have.

Now, look at this improved version: "You are the assistant for Belleza Total, an aesthetics center in Caballito. We offer manicures ($800), pedicures ($900), and laser hair removal ($1200 per session). Our tone is warm and professional. Reply in Rioplatense Spanish. We're open Monday to Saturday from 9:00 to 18:00. If someone asks for an appointment, offer the available time slots and confirm with the client. If they ask about prices, send the updated list. If the client wants a service we don't offer, suggest alternatives. If there's a complaint or something you don't know, transfer to a human agent. Don't make up information."

The difference is huge. The first prompt leaves everything to the AI's imagination. The second gives it context, concrete data, tone, and limits. The result: useful responses, consistent with your brand, that don't make up prices or services.

Adapt this example to your business. It doesn't have to be perfect the first time; start with what you know and adjust over time.

Common mistakes and how to avoid them

Mistake number one is thinking that AI reads your mind. If you don't give it context, it will improvise. Another classic: not defining limits. If you don't tell it what NOT to do, it can promise things you can't deliver, like discounts that don't exist or deliveries you don't make.

There's also the mistake of overloading the prompt. You want the AI to know everything, but an endless, disorganized prompt confuses more than it helps. Organize the information into clear sections and prioritize what's really important.

A very common mistake in practice: not updating the prompt when something changes. If you launched a new product or changed your hours, the AI will keep responding with old data. And that shows, and the customer notices it.

The solution is simple: treat the prompt like a living document. Review it every month, adjust what isn't working, and test small changes. Don't be afraid to iterate: AI is flexible, and you should be too.

• Don't assume the AI knows your business: give it context.
• Define clear limits on what the AI should not do.
• Update the prompt when your business changes.
• Organize the information so you don't overwhelm the AI.

How to measure if your prompt is working

Writing a good prompt isn't enough: you need to know if it's working. The most direct metric is the approval rate of responses. If in Wando you approve most of the AI's suggestions, it's a sign that the prompt is aligned with your style. If you reject them often, it needs adjusting.

Another useful metric is response time. If the AI saves you minutes in every conversation, the prompt is meeting its goal. Also look at customer satisfaction: if you receive fewer complaints and more resolved inquiries, you're on the right track.

Pay attention to error patterns. Does the AI make up prices? Does it give overly long answers? Does it fail to escalate when it should? Each pattern tells you which part of the prompt needs more clarity. For example, if it makes up prices, add a line that says "don't make up prices, use only the ones I give you".

Finally, compare with a human team. If agents resolve queries that the AI cannot, it's an opportunity to improve the prompt with that information. AI doesn't replace your team: it empowers it.

• Approval rate of suggested responses.
• Average response time.
• Recurring error patterns.
• Comparison with resolution by human agents.