# Sandbox.UI.Panel.OnTooltip

```csharp
System.Action<Panel> OnTooltip { get; set; }
```

Build a richer tooltip than a line of text. Called with the tooltip panel as it's about to be
shown - add whatever it should contain: labels, images, anything. If [Sandbox.UI.Panel.Tooltip](/api/Sandbox.UI.Panel/Tooltip) is
set too, that text is already in there as the first child.

Declared in [Sandbox.UI.Panel](/api/Sandbox.UI.Panel).
Assembly: `Sandbox.Engine`.