> ## Documentation Index
> Fetch the complete documentation index at: https://productbrain.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Rail

> Right-side context for the focused entry.

<Warning>
  **Early access** — [**Join the Product Brain Community**](https://community.productbrain.io).
</Warning>

Rail holds context: card → rail → page. Agents approximate with MCP `entries` + `relations`.

Screenshot: **coming soon**.