The WhatsApp Business API is the only official way to let an AI agent reply to customers on your number, and getting it ready takes longer than building the agent. Most delays come from Meta's approvals and a few rules about when you're allowed to message someone, not from the code.
Here's what we check before a WhatsApp agent talks to a real customer.
What the WhatsApp Business API needs before an AI agent can use it
The WhatsApp Business app on your phone is built for a person typing replies. An agent can't log into it. The API is a separate door: your server receives each incoming message as a webhook and sends replies back through Meta's Cloud API, or through a provider that sits on top of it.
Before you go live you need four things in place:
- A Meta business account, verified with your company's legal details. You can start testing before it's verified, but until verification is approved you can only message a small number of customers a day.
- A phone number registered for the API. Check Meta's current rules on whether that number can also stay in the regular app, because this has changed over time.
- An approved display name that matches your business.
- A payment method on the Meta account, since Meta bills for some message types.
Start the verification on day one. It's the one step you can't speed up by working harder, and it's where small businesses most often lose a week. If your documents don't match the name on the account exactly, expect a rejection and a restart.
Keep the agent about your business. Since January 2026, Meta's terms don't allow general-purpose AI assistants on the WhatsApp Business API. An agent that answers questions about your services, takes bookings and handles support is fine; one that will chat about anything isn't.
The 24-hour window and message templates
This rule shapes the whole design. When a customer messages you, a 24-hour window opens. Inside it your agent can reply with any text it likes. Once it closes, you can only send a pre-approved template message.
That matters for anything the agent starts itself: a booking reminder, a payment link that wasn't paid, a follow-up the next day. Each one has to be a template that Meta has already approved, with fixed wording and placeholders for the changing parts (name, date, amount).
Templates fall into categories such as utility (a booking confirmation), marketing and authentication. Meta decides the category, not you, and the category affects what you're charged per message. Write a reminder that sounds like a promotion and it may be classed as marketing.
Our advice: write your templates before you write the agent. List every message the business sends outside a conversation, submit them early, and design the agent around what's approved. Approval can take minutes or a couple of days.
How the agent connects to bookings, calendars and payments
The agent itself is usually a language model with a few tools it can call: check availability, create a booking, send a payment link. WhatsApp is just the channel.
We built one for PureMotions, a car-rental business. Its agent replies in the customer's language, checks which cars are free, sends a Stripe payment link in the chat and confirms the booking, at any hour. The part customers see is a chat. The part that makes it work is that the agent checks real availability before it offers a car. We cover the full flow in our post on how a WhatsApp AI booking agent works.
Two details trip people up:
Webhooks arrive more than once
Meta resends a webhook if your server doesn't answer quickly with a 200. If your agent takes too long to reply to the webhook, Meta sends it again, and you can end up sending two replies or creating two bookings. Reply to the webhook straight away, store the message ID, and ignore any ID you've already handled. Do the slow work in the background.
Payments need a paper trail
Don't mark a booking as paid because the customer said "done". Confirm it from the payment provider's own webhook, then send the WhatsApp confirmation. The chat is a conversation. The payment record is the proof.
Opt-in, quality rating and sending limits
You need the customer's permission before you message them first. A person writing to you counts for the 24-hour window, but a template sent to someone who never contacted you needs a clear opt-in, such as a checkbox on your booking form. If you serve customers in the EU, ask your lawyer how GDPR applies to your message logs and the AI provider that processes them.
Meta also gives each number a quality rating based on how people react. If many customers block or report your messages, the rating drops and your daily sending limit with it. New numbers start with a low limit that rises as you send good messages. So don't launch with a mass broadcast to your whole contact list. Start with customers who are already in a conversation.
What happens when the agent gets it wrong
An agent will meet questions it shouldn't answer: a refund dispute, an angry customer, a request that doesn't fit your rules. Decide in advance what it does then.
- Give it a clear list of what it's allowed to do, and have it say so plainly when a request is outside that list.
- Add a handoff: a keyword or a trigger that sends the conversation to a person, with the chat history attached.
- Let someone on your team see the live conversations for the first two weeks.
- Log every message the agent sends so you can find out what happened when a customer complains.
Test it with ugly inputs before launch. Voice notes, photos, messages in the wrong language, three questions in one message, and someone writing "cancel" when they mean something else.
A short go-live list
- Business verification is approved and the display name is accepted.
- Every outbound message has an approved template.
- Webhooks reply fast and ignore duplicates.
- Payments are confirmed by the payment provider, not by the chat.
- Opt-in is recorded for anyone you message first.
- A person can take over any conversation.
- Your first week's volume is small enough to watch by hand.
If you'd like help with the approvals, the agent or the calendar and payment connections, see our AI apps and agents service or get in touch and tell us what your business needs the agent to do.