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Use cases / Agents that send messages

Once your agent sends an email, you can’t take it back.

When an agent can send emails or post messages, one wrong send reaches people before anyone can stop it. Here is what you can do yourself, and how Stackduke holds a send for a person.

Join the waitlistWhat Stackduke covers
One email on its way to 4,212 recipients, waiting at a checkAn Agent sends one email towards a large field of recipients. A Stackduke rule holds every send from this agent, so the email stops at the check and waits for a person. None of the 4,212 recipients has received it. One recipient, the customer the reply was meant for, is lit.AGENTSTACKDUKERULE: HOLD EVERY SENDSEND_EMAILWAITS FOR A PERSON4,212 RECIPIENTSNOT REACHEDTHE ONE CUSTOMER

Why it goes wrong

A sent message stays sent.

Once a message is delivered, it is out of your hands: a promise the agent should not have made, a draft that went to the whole list, or a reply with another customer’s details in it.

There is no undo

You cannot pull a delivered email or chat message back from the people who read it. All you can do is send another one.

The address list is the risk

Replying to one customer and emailing every customer can be the same tool. Only the list of addresses is different.

Too many approvals get skipped

If every message waits for a person, people stop reading what they approve. We recommend letting the agent write drafts freely and holding only the send.

An illustration

One refund email, sent to 4,212 people.

This is an illustration, not a reported incident. It shows the shape of the mistake: the right tool, the right words, the wrong people.

With Stackduke

Your agent writes it. A person sends it.

Stackduke checks each call, and who it is going to, before it reaches your email service. Your rule says every email this agent sends waits for a person, so someone on your team sees the message and all 4,212 addresses before anything goes out. A rule cannot count the addresses, so every send waits, not only the big ones. Writing a draft is a different tool, so drafts are not held.

What it covers

What Stackduke covers.

Stackduke

Each MCP call is checked against your rules before it runs.

  • Your agent’s MCP calls go through Stackduke, so each send is checked before it reaches your email service.
  • A send waits for a person, with the message and every address in view.
  • A person approves the exact message they saw, and only that message goes out.

Free tools

Open source or public, and free to use.

  • The open-source scanner labels each tool a server offers, so you can see which ones send.
  • The tracker shows what changes in the MCP servers it follows, including new tools that send.

Not covered

Stackduke does not do these. Plan for them another way.

  • Holding only the big sends. A rule cannot count addresses, so it holds every send from that agent.
  • Judging what a message says. Stackduke does not check whether the words are right.
  • Removing private details from what an agent sends.
  • Data leaving another way, such as in a search or a link the agent opens.

What you can do now

What you can do yourself.

None of this needs Stackduke. We recommend all three before giving an agent a tool that sends.

Before an agent gets a tool that sends3 steps

  1. Give the agent a tool that writes drafts, where your email service has one, and let a person press send.

  2. Turn on tool approval in the app your agent runs in, for the tools that send, so each send waits for you.

  3. Send from an account that can only reach the people the agent should reach, such as one shared inbox, not your whole contact list.

Go deeper

Further reading

  • Concept

    How approvals work

    What a person sees when a call waits for them, and what their approval covers.

Let agents write. Decide what gets sent.

Join the waitlist to try it.

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