DEV Community: M91

M91: Human-in-the-Loop (HITL) Alerts for Software Approvals

M91 — Thu, 29 Oct 2026 09:57:45 +0000

Software and AI agents can do most work on their own. But some steps need a person to say "yes" or "no" first.

Think of a big refund, a risky deploy, or an AI agent about to delete data. The software should stop and ask a human.

But most tools ask by email, chat, or SMS. Those messages arrive quietly and just wait. If the right person is asleep or busy, the approval waits too.

M91 fixes that. It rings the right person's phone until someone answers, then sends the answer back to your software.

Quick answer: When your software needs a human approval, M91 turns the request into a loud phone alert with buttons like "Approve" and "Reject." It rings even on silent, keeps going until someone answers, and sends the answer back to your software.

In this guide, you will learn:

What M91 is, and what human-in-the-loop (HITL) means
Why approvals get missed today
How M91 works in 3 simple steps
What happens when an alert is sent

Your software asks. A person answers.

What Is M91?

M91 is a free human-in-the-loop alerting app made by MSG91. When software or an AI agent needs a decision, it rings the right person's phone, even on silent, until someone answers. Then it sends the answer back.

What Is Human-in-the-Loop (HITL)?

Human-in-the-loop (HITL) means the software does the work, but a person decides at the important steps.

There are three common kinds of HITL steps:

Human approval: a person says "yes" or "no" before the software continues.
Human review: a person checks something before it goes out.
Human takeover: a person steps in when the software or AI agent gets stuck.

The hard part of HITL isn't the decision. It's reaching the right person in time. That's the gap M91 fills.

The Problem: Approvals Get Missed

Here's a common example. A big refund needs a manager's approval at night. The system sends an email. The manager sees it the next morning. By then, the customer is upset.

Nothing broke. The message was just too quiet.

Email, chat, and SMS are fine for updates. They are the wrong tool when someone has to act now.

How M91 Works in 3 Simple Steps

Create a channel. A channel is a group of people who get the same alerts, like your on-call team or your managers.
Invite people by phone number. Each person installs M91, signs in, allows notifications, and accepts the invite.
Copy the channel's send link. Find it on the channel screen and tap the copy icon.

That one link is the whole integration. When your software opens the link with a title, M91 sends the alert.

You can use the link almost anywhere: a browser, a cron job, a monitoring tool, a spreadsheet, your own code, or an AI agent. Using a workflow tool like viaSocket, n8n, Zapier, or Make? Just add one HTTP step to your approval workflow.

No SDK. No API key. No code needed.

Keep the send link secret, like a password. Anyone who has it can ring your whole team.

Want to try it safely first? Tap Send a test alert in the app, or follow this guide: How to Test Your M91 Alert Link Without Waking Anyone.

Three steps. One link. No code.

What Happens When an Alert Is Sent?

Every phone in the channel rings. It rings at full volume, even on silent mode and Do Not Disturb.
It keeps trying until someone answers. One quiet buzz is not enough for urgent work.
No answer? M91 calls. HIGH and CRITICAL alerts escalate to a phone call if nobody responds.
The answer goes back to your software. M91 records who answered, what they chose, and when.

If nobody ever answers, M91 tells the channel owner and keeps the alert open. "We stopped trying" is not the same as "handled."

M91 keeps trying until a real person answers.

Approve, Reject, or Take Over: You Choose the Buttons

You write the reply buttons in your own words. For example:

"Approve"
"Reject"
"I'm on it"
"Seen"

That's a full human approval workflow in a few buttons. Your AI agent can even choose its own buttons, like "Ask for receipt."

Each button does one of two things:

"I'll take this." One person taps it, and every other phone stops ringing. This is how a human takeover works.
"I've seen it, but it's not mine." The answer counts only for that person. The alert stays open for everyone else.

A button can also ask for proof. For example, the "Reject" button can ask for a short note, or a "Done" button can ask for a photo.

Your buttons. Your words.

M91 Only Rings When It Should

An alert app should stay quiet until it's really needed. M91 keeps the noise down in three ways:

You pick how urgent it is. A LOW alert rings once. A CRITICAL alert keeps ringing and calls people.
Repeats collapse into one. The same problem won't wake your team five times.
Handled means handled. Once someone takes the alert, it stops ringing on every other phone.

An alert nobody hears is just a log entry.

One problem. One alert. One answer.

Who Uses M91?

M91 works anywhere a person must act, and it can't wait until morning.

AI agents: an agent is about to do something it can't decide alone, like deleting customer records.
Payments: card payments are failing and nobody is watching the dashboard.
Infrastructure: a server breaks at 2 AM and an engineer needs to wake up.
Devices and IoT: a warehouse door is left open and someone must go check.
Customer support: a bot runs out of answers and a customer wants a real person.
Sales and CRM: a big lead replies and needs an owner fast.

Email vs. Chat vs. M91

	Email	Team chat	M91
Built to...	Wait	Wait	Reach someone now
Rings through silent mode and Do Not Disturb	No	No	Yes
Keeps going until someone answers	No	No	Yes
Calls if nobody responds	No	No	Yes, for HIGH and CRITICAL
Sends the answer back to your software	No	No	Yes

Get Started With M91

Download the M91 app from m91.msg91.com.
Create a channel and invite yourself.
Tap Send a test alert and watch your phone ring.

If your phone rings, you're ready to add a human-in-the-loop step to your software.

👉 Get M91 free and send your first alert

Frequently Asked Questions

What is M91?

M91 is a free human-in-the-loop alerting app made by MSG91. When software or an AI agent needs a decision, it rings the right person's phone, even on silent, until someone answers. Then it sends the answer back.

What is HITL?

HITL stands for human-in-the-loop. The software does the work, but a person approves, reviews, or takes over at the important steps. M91 makes sure that person gets the alert and answers it.

What is a human takeover?

A human takeover is when a person steps in to handle something software or an AI agent can't finish. In M91, one person taps a button like "I'm on it," and every other phone stops ringing.

How do I add human approval to an automation or AI agent?

Create an M91 channel, invite your approvers, and copy the send link. When your automation or AI agent calls that link, the approvers' phones ring. Their answer, like "Approve" or "Reject," goes back to your software.

Do I need to write code?

No. Every channel has a send link. You can open it from a browser, add it as an HTTP step in a workflow tool, or paste M91's setup prompt into your coding agent.

What happens if nobody answers?

M91 keeps trying. HIGH and CRITICAL alerts escalate to a phone call. If nobody ever answers, the channel owner is told and the alert stays open.

Does M91 ring when my phone is on silent?

Yes. An M91 alert breaks through silent mode and Do Not Disturb on iPhone and Android. You just need to allow M91's notifications.

Will M91 send repeat alerts for the same problem?

No. Repeats of the same problem collapse into one alert, so your team isn't woken twice.

Is M91 free?

Yes. M91 is free forever. Every feature, every alert, and every person on your team is included.

Where can I get M91?

M91 is on iPhone and Android. Get it from m91.msg91.com.

Step-by-Step: How to Test Your M91 Alert Link Without Waking Anyone

M91 — Thu, 29 Oct 2026 06:50:52 +0000

Want to test your M91 alert link? Here is the safe way to do it, step by step.

M91 alerts are loud. A real alert rings every phone on your team. It rings at full volume, even on silent.

So how do you test it without waking everyone up?

It's easy. Open the link with nothing added to the end. M91 checks the link, and no phone rings.

Quick answer: To test an M91 alert link safely, open the link with nothing added after it. M91 shows your channel's name. No phone rings. Add a title only when you want a real alert.

In this guide, you will learn how to:

Check your alert link without ringing any phone
Fix a link that doesn't work
Send one small test alert
Make sure your team really got it

What Is M91?

M91 is a free app made by MSG91. It rings a real person's phone when software needs help.

Here is how it works. You make a group of people in M91. This group is called a channel. Every channel gets its own special link. It's called the send link.

When your software opens that link with a message, every phone in the channel rings. It keeps ringing until someone answers.

What Is Human-in-the-Loop (HITL)?

Human-in-the-loop (HITL) means the software does the work, but a person steps in when it really matters. For example:

Human approval: a person says "yes" or "no" before a big refund.
Human review: a person checks something before it goes out.
Human takeover: a person takes over when an AI agent gets stuck.

M91 is how your app, your approval workflow, or your AI agent reaches that person. You don't need an SDK or an API key. You only need the send link.

How to Find Your M91 Send Link

Open your channel in the M91 app.
Look for the send link on the channel screen.
Tap the copy icon.

Keep this link secret, like a password. Anyone who has it can ring your whole team.

Why Should You Test Your Alert Link?

Think about mailing a birthday card. You check the address first. If the address is wrong, the card never arrives.

Your alert link is the same. Testing is the last part of your alert link setup. A quick test shows you if:

The link was copied the right way
The link goes to the right channel
Your team can really get the alert

It only takes a minute. And it can save you from a missed alert in the middle of the night.

How to Test Your M91 Alert Link in 6 Easy Steps

Step 1: Check the Link (No Phone Rings)

Open your send link in your web browser, exactly as you copied it. Add nothing to the end.

M91 shows your channel's name. No phone rings. This is called a connection test.

Why doesn't it ring? Many apps open links on their own to make little previews. If a plain link rang phones, just pasting it in a chat could wake your team. So M91 only rings when a message title is added.

Check this: Do you see the right channel name? Great! Go to Step 2.

Watch out: Does your link end with ?title=? Delete everything from the ? onward first. A link with a title is a real alert. It will ring everyone.

Step 2: Fix the Link If Something Looks Wrong

Did something look odd in Step 1? Here's what it means and how to fix it.

You see a different channel's name. You copied the link from the wrong channel. Copy it again from the right one.
You see "401" or "UNAUTHORIZED". The link is wrong or cut short. Copy it again and paste all of it. Don't add a / at the end.
Your link starts with https://m91.msg91.com/s/. That's an old address. Change the start to https://m91-api.msg91.com/s/. Keep the rest the same.
Nothing shows up at all. Your computer can't reach M91. Check your internet. The link itself is fine.

Step 3: Make Sure Everyone Has Joined

This is the number one reason an alert reaches nobody.

Getting an invite is not the same as joining. Each person must do 3 things:

Install M91 and sign in with the phone number you invited.
Allow notifications, so the alert can reach them.
Accept the invite.

Now check. Open the channel and tap the people icon. You'll see the Members list. Everyone should say ACCEPTED, not INVITED.

Did someone reinstall the app? They should open it once. That connects their phone again.

Step 4: Send One Small Test Alert

Now let's hear it ring. This time, it's a real test alert.

First, tell your team. Say: "Test alert at 3 PM. Please tap the button." It will ring loudly, even on silent.

The easiest way: In the M91 app, tap Send a test alert on the channel screen. Everyone in the channel gets it.

The no-code way: Add this to the end of your send link. Then open it in your web browser.

?title=Test%20alert%20from%20setup&severity=LOW&respond=Got%20it&customId=setup-test

What do these words mean?

title is the message people see on their phone. It needs at least 5 characters.
severity=LOW makes it gentle. A LOW alert rings once. It never phones anyone.
respond=Got it adds a "Got it" button.
customId=setup-test gives the alert a name, so you can find it later.

Your browser will show a simple page. That's normal.

Step 5: Check That Your Team Got It

The simplest check is to ask your team: "Did your phone ring?"

Here's what to do if something went wrong:

Nobody's phone rang. People haven't finished joining. Go back to Step 3.
One phone stayed quiet. That person should turn on notifications for M91. Then they open the app again.
Your second test didn't ring. You sent the same test within 5 seconds, or your first test is still open. Change the title a little, or close the first test. Then try again.

Using code? M91's reply has a number called delivered. It tells you how many phones got the alert. If it's 0, go back to Step 3.

Step 6: Answer It, Then Close It

Tap the button on your phone. An answer coming back is the only real proof that someone saw the alert.

M91 keeps an alert open until someone closes it. This is true even after someone answers. So when you're done, open the alert in the app and tap Close alert.

That's it. Your test is complete!

Answer it, see it, close it.

Quick Checklist: Is Your M91 Alert Link Ready?

✅ I copied the link from my channel, with nothing added
✅ The connection test showed the right channel name, and no phone rang
✅ Everyone installed M91, allowed notifications, and says ACCEPTED
✅ I told my team before the real test
✅ I sent one test alert, and the phones rang
✅ Someone tapped the answer, and it came back
✅ I closed the test alert

All done? Your alert link setup is complete!

What's Next? Add Human Approval to Your App or AI Agent

Your link works. Now add a human-in-the-loop step where your software needs a person.

Human approval: Add "Approve" and "Reject" buttons. Use them before a refund, a payment, or anything risky.
Human takeover: Add a "Take over" button. Use it when a bot or AI agent gets stuck and a customer wants a real person.
Urgent phone alerts: Use HIGH or CRITICAL for problems that can't wait. A HIGH alert escalates to a phone call only if nobody answers or even opens it. A CRITICAL alert keeps ringing and escalates to phone calls.

New to M91? Read What Happens When Your Software Needs a Human Approval?

Want to see how an answer gets back to your software? Read How the M91 Alert Flow Moves an Alert From Software to a Person.

👉 Get M91 free and test your first alert link

For Developers: The Same Test in Code

Prefer the terminal? Here are the same steps. Replace YOUR_SEND_LINK with your send link.

1. Connection test (no phone rings):

curl -sS "YOUR_SEND_LINK"

2. Send one LOW test alert:

curl -sS -X POST "YOUR_SEND_LINK" \
  -H "Content-Type: application/json" \
  -d '{
    "title": "Test alert from M91 setup. Please tap Got it.",
    "severity": "LOW",
    "customId": "setup-test",
    "responseOptions": [{"label": "Got it", "effect": "SHARED"}]
  }'

3. Read the answer (decision stays null until someone taps):

curl -sS "YOUR_SEND_LINK/alerts/setup-test"

4. Close the test alert (a 404 or 403 here just means it's already closed):

curl -sS -X POST "YOUR_SEND_LINK/close" \
  -H "Content-Type: application/json" \
  -d '{"customId": "setup-test"}'

Frequently Asked Questions

How do I test an M91 alert link without waking anyone?

Open your M91 send link with nothing added to the end. M91 shows your channel's name. No phone rings. This is called a connection test.

What is the M91 connection test?

It's a safe way to check your send link. A plain link, with no title, does not send an alert. It only tells you the link works and which channel it belongs to.

Does opening the M91 alert link in a browser send an alert?

Only if the link has a title. A plain link is just a connection test. A link with ?title= sends a real alert and rings every phone in the channel.

Can I test M91 without writing code?

Yes. Tap Send a test alert in the M91 app. Or add ?title= and &severity=LOW to your link and open it in your browser.

Why did my test alert reach nobody?

Usually, people were invited but didn't finish joining. Each person must install M91, sign in, allow notifications, and accept the invite.

Why didn't my second test alert ring?

Either you sent the same test within 5 seconds, or the first test is still open. Change the title a little, or close the first test. Then try again.

What severity should I use for a test alert?

Use LOW. It rings once and never phones anyone.

Is the M91 send link secret?

Yes. Keep it safe, like a password. Anyone who has it can ring your whole team.

Is M91 free?

Yes. M91 is free forever. Every feature, every alert, and every person on your team is included.

Should I test M91 before adding it to an AI agent or approval workflow?

Yes. Run the connection test, send one test alert, and get an answer back. Then your human-in-the-loop (HITL) step for human approval or human takeover will work when it really matters.

DEV Community: M91

M91: Human-in-the-Loop (HITL) Alerts for Software Approvals

What Is M91?

What Is Human-in-the-Loop (HITL)?

The Problem: Approvals Get Missed

How M91 Works in 3 Simple Steps

What Happens When an Alert Is Sent?

Approve, Reject, or Take Over: You Choose the Buttons

M91 Only Rings When It Should

Who Uses M91?

Email vs. Chat vs. M91

Get Started With M91

Read Next

Frequently Asked Questions

What is M91?

What is HITL?

What is a human takeover?

How do I add human approval to an automation or AI agent?

Do I need to write code?

What happens if nobody answers?

Does M91 ring when my phone is on silent?

Will M91 send repeat alerts for the same problem?

Is M91 free?

Where can I get M91?

Step-by-Step: How to Test Your M91 Alert Link Without Waking Anyone

What Is M91?

What Is Human-in-the-Loop (HITL)?

How to Find Your M91 Send Link

Why Should You Test Your Alert Link?

How to Test Your M91 Alert Link in 6 Easy Steps

Step 1: Check the Link (No Phone Rings)

Step 2: Fix the Link If Something Looks Wrong

Step 3: Make Sure Everyone Has Joined

Step 4: Send One Small Test Alert

Step 5: Check That Your Team Got It

Step 6: Answer It, Then Close It

Quick Checklist: Is Your M91 Alert Link Ready?

What's Next? Add Human Approval to Your App or AI Agent

For Developers: The Same Test in Code

Frequently Asked Questions

How do I test an M91 alert link without waking anyone?

What is the M91 connection test?

Does opening the M91 alert link in a browser send an alert?

Can I test M91 without writing code?

Why did my test alert reach nobody?

Why didn't my second test alert ring?

What severity should I use for a test alert?

Is the M91 send link secret?

Is M91 free?

Should I test M91 before adding it to an AI agent or approval workflow?