> For the complete documentation index, see [llms.txt](https://support.referralhero.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.referralhero.com/settings/security/blacklist.md).
# Blacklist
If you want to exclude specific domains from signing up onto your list. You can easily achieve this by adding such domains to your blacklist, which you can find under *Settings > Anti-fraud*.
Just add one domain per line and make sure you only add the domain name and extension, without `www` or `http`
* ❌
* ❌ [www.mydomain.com](http://www.mydomain.com)
* ✅ mydomain.com
After you add a domain to the blacklist, people who try to sign up using that domain will get a "*This domain is not valid.*" error.
**NOTE**: Blacklist is currently a PRO and Premium feature.
---
# Agent Instructions
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## Querying This Documentation
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Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
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```
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