> For the complete documentation index, see [llms.txt](https://docs.kerberus.com/kerberus/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.kerberus.com/kerberus/frequently-asked-questions/software-faq/is-there-a-cost-to-use-sentinel3.md).
# Is there a cost to use Sentinel3?
When you install Kerberus Sentinel3 you are enrolled by default into the Pro version.
In the Pro version we charge a small fee on some swaps on select DEXes. You can read more in our [**Terms of Use**](https://www.kerberus.com/terms-of-use/).
You can downgrade to the Free version at any time by clicking in your Sentinel3 extension on your browser, Settings, Downgrade to Free.
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# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://docs.kerberus.com/kerberus/frequently-asked-questions/software-faq/is-there-a-cost-to-use-sentinel3.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
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Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.