# Agency WhatsApp API: every client, no Meta onboarding?

> One API, n8n node and MCP server for all your clients: WhatsApp, email and SMS from their own number and mailbox. No Meta setup, no per-message fee.

Source: https://unlimitedmessaging.app/articles/marketing-agency-whatsapp-api-clients

Agencies · Freelancers · WhatsApp · Email · SMS

# One integration,  
_every client's own number._

Your client scans a QR code once. From then on, your n8n workflows, your code or Claude send WhatsApp, email and SMS from their number and their mailbox, with no Meta Business verification and no per-message bill to pass on.

[Start for free](https://app.unlimitedmessaging.app)[See the WhatsApp channel](https://unlimitedmessaging.app/channels/whatsapp)

An agency's month

## Twelve clients, twelve WhatsApp setups to babysit

Unlimited Messaging is a messaging API that lets an agency or a freelancer send WhatsApp, email and SMS on behalf of each client, from that client's own WhatsApp number, mailbox and phone, through one REST API, one n8n node and one MCP server.

A dentist wants lead forms answered on WhatsApp. A shop wants order updates. A coach wants a reminder before every call. With the official WhatsApp Cloud API, each of them means a Meta Business portfolio, an Embedded Signup flow, approved templates and a card on file, because Meta bills every delivered template message since July 1, 2025\. The setup often takes longer than the automation.

With Unlimited Messaging, the client links their existing WhatsApp by scanning a QR code, like WhatsApp Web, and their mailbox over IMAP/SMTP. You build once: the same API call or n8n node serves every client, you only change the account it sends from. Replies come back in the app, or to your webhook on paid plans.

Same building blocks for [freelancers who let Claude reply](https://unlimitedmessaging.app/articles/freelance-claude-answers-whatsapp) and for [e-commerce order updates](https://unlimitedmessaging.app/articles/ecommerce-order-notifications-whatsapp-sms). The channel is explained on [the WhatsApp page](https://unlimitedmessaging.app/channels/whatsapp).

![Drawing of the Unlimited Messaging app showing a log of webhook events, each answered with 200, with the headline “One workflow, every client's number”.](https://unlimitedmessaging.app/_next/image?url=%2Fassets%2Farticles%2Fcovers%2Fmarketing-agency-whatsapp-api-clients-en.png&w=3840&q=75)

Definition
Multi-client messaging API

One API account holding the WhatsApp numbers, mailboxes and SMS phones of several clients, where each request names the account it sends from, so one integration serves every client.

WhatsApp API for agencies, multi-tenant WhatsApp API, white label WhatsApp automation, reseller messaging API

What changes

## What Unlimited Messaging changes for an agency

Less onboarding per client, one integration to maintain, and a price that does not grow with each message your clients send.

1. 01  
### No Meta onboarding per client  
No Business verification, no template approval, no Embedded Signup. The client scans a QR code from WhatsApp on their phone, in person or over a video call, and the number is live.
2. 02  
### One integration, every account  
Every account gets an id. Your workflow passes the client's accountId and the same POST /message sends WhatsApp, email or SMS, or all three in one request.
3. 03  
### Your tools: n8n, SDKs, MCP  
Use the official n8n node, the TypeScript or Python SDK, or the hosted MCP server so Claude or ChatGPT can draft and send for a client after approval.
4. 04  
### A flat price, not a meter  
Messages are unlimited on every plan, so a busy client does not raise your bill. The free plan adds a short footer; Medium at €19/month removes it and adds webhooks and media.

Setup

## Your first client live in 3 steps

1. 01  
### Create one account  
Free sign-up, no credit card. Generate an API key, or connect n8n or your AI assistant.
2. 02  
### Link the client's channels  
The client scans the WhatsApp QR code from their phone. Add their mailbox over IMAP/SMTP, and their Android phone through the free app if they want SMS.
3. 03  
### Reuse your workflow  
Duplicate your n8n workflow or call the API with the client's accountId. Point replies to the client's CRM through a webhook on a paid plan.

Copy-ready messages

## 5 messages agencies automate for clients

Replace what is in brackets. Each one leaves from the client's own number or address, so customers recognise the business, not your agency.

1. 01 · WhatsApp  
### Instant reply to a web form lead  
Hi \[First name\], thanks for your request on \[website\]. I'm \[Name\] from \[Business\]. Could you tell me a bit more about \[need\]? A good time to call you back?
2. 02 · WhatsApp  
### Appointment confirmation  
Hi \[First name\], your appointment at \[Business\] is confirmed for \[day\] at \[time\], \[address\]. Need to change it? Just reply here.
3. 03 · Email  
### Quote follow-up after 3 days  
Hello \[First name\], I'm following up on the quote sent on \[date\] for \[service\]. Do you have any questions, or would you like to adjust something? Best regards, \[Name\], \[Business\]
4. 04 · SMS  
### Review request after a visit  
Thanks for visiting \[Business\] today, \[First name\]. If you have 30 seconds, a review helps us a lot: \[link\]. \[Business\]
5. 05 · Email  
### Note to the client before linking  
Hi \[Client name\], To connect your WhatsApp, open WhatsApp on your phone, go to Linked devices and scan the QR code I'll share on our call. Your number stays yours and keeps working on your phone as usual. \[Your name\], \[Agency\]

Good to know

## When this fits, and when it does not

1. 01  
### Customers who know the business  
WhatsApp is linked as a device, not through Meta's official API. Messages to leads and customers who wrote first are fine; cold bulk campaigns get a number banned, whatever the tool.
2. 02  
### Large broadcasts belong to the Cloud API  
A client sending promotions to tens of thousands of opted-in contacts, or who needs a green verified badge, should use Meta's official Cloud API with approved templates.
3. 03  
### Free plan for testing  
Free messages carry a "Sent with UnlimitedMessaging.app" footer, and media and webhooks are paid-only. For client work, plan on Medium or Max.

Key takeaway

### Build the automation once, plug in each client by QR code

One API, one n8n node and one MCP server cover every client. Each message leaves from the client's own number or mailbox, and the price stays flat however much they send.

FAQ

## Questions agencies ask

No. Their existing WhatsApp or WhatsApp Business app is linked as a connected device by QR code. There is no Business verification, no template approval and no Meta billing to set up.

Yes. One account holds several WhatsApp numbers, mailboxes and SMS phones. Each request names the account it sends from with accountId, so one workflow serves every client.

Yes. The link works like WhatsApp Web: the client keeps chatting from their phone and sees the messages your automation sends.

The free plan is permanent, needs no credit card and has no per-message fee, but messages carry a short "Sent with UnlimitedMessaging.app" footer. Medium (€19/month) and Max (€29/month) remove the footer.

Yes, on Medium and Max: every incoming message triggers a webhook to the URL you choose, or an n8n workflow. On the free plan, replies show in the in-app inbox.

No. Unlimited Messaging uses WhatsApp's linked-device protocol, not Meta's Cloud API. That is why there are no templates or per-message fees, and also why it suits conversations with known contacts rather than mass marketing.

Sources

## Sources & references

To check the information in this article for yourself:

1. [01Get started as a Tech Provider↗Meta](https://developers.facebook.com/docs/whatsapp/solution-providers/get-started-for-tech-providers)
2. [02WhatsApp Business Platform pricing↗Meta](https://developers.facebook.com/docs/whatsapp/pricing)
3. [03WhatsApp Terms of Service↗WhatsApp](https://www.whatsapp.com/legal/terms-of-service)
4. [04n8n documentation↗n8n](https://docs.n8n.io/)
5. [05Model Context Protocol↗Anthropic](https://modelcontextprotocol.io/)

![Ilian, senior software engineer](https://ilianazz.com/images/iliazz.png)

Written by

[Ilian](https://unlimitedmessaging.app/authors/ilian) · Senior Software Engineer

A senior software engineer, he founds and runs several tech companies. He builds products around messaging APIs, automation and AI integration, and shares here what he learns while building.

[View LinkedIn profile↗](https://www.linkedin.com/in/ilianAzz/)Updated November 9, 2026

![](https://unlimitedmessaging.app/assets/logos/whatsapp.svg)![](https://unlimitedmessaging.app/assets/logos/email.svg)![](https://unlimitedmessaging.app/assets/logos/sms.svg)

## Wire up your first client this afternoon

Free, no credit card. One QR code scan and your workflow sends from their number.

[Start for free→](https://app.unlimitedmessaging.app)

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