> For the complete documentation index, see [llms.txt](https://docs.zaia.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.zaia.app/tools/available-tools/external-user-blocking-tool.md).

# External User Blocking Tool

Use the **External User Blocking Tool** to stop confirmed bot-to-bot conversations.

The tool is native to the main chat Agent. It has no configuration or input fields.

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### 🔎 When the tool is available

The tool is available only during a main chat flow. It requires a chat owned by an external user.

It supports these channels:

* Instagram
* Telegram
* WhatsApp, including Waha
* Widget

The tool is unavailable for API and Zaia channels. It is also unavailable outside chat context.

### 🛡️ When to use it

Use this tool only when the Agent has absolute certainty that it is talking to another bot.

Do not use it for suspected automation or ambiguous behavior. Blocking stops future messages from that external user.

{% hint style="warning" %}
The certainty requirement is guided by the tool instruction. It is not enforced by a separate blocking rule.
{% endhint %}

### ⚙️ What happens when the Agent blocks a user

The system resolves the target from the current chat owner. The Agent cannot choose or provide another user.

Before blocking, the system confirms that:

* The external user exists in the workspace.
* The external user owns the current chat.

If the user is already blocked, the tool succeeds without changes. Otherwise, it marks the external user as blocked.

The chat updates immediately in the interface. The workspace owner also receives an email notification.

### 📬 Owner notification

The notification identifies the blocked external user by ID. It directs the owner to locate that user in **Inbox → Chat History**.

The email does not include a direct link to the chat.

### ✅ Result

After the user is blocked, existing platform rules reject new messages from that user. This prevents the automated exchange from continuing.

The workspace owner can review the event in Chat History.