By default, scripts are marked for execution whenever a parameter or the script itself changes. The Unbound Input parameter category is meant for parameters that are used inside a script.

For scripts that should execute with every model update even if no parameters have changed, set the Update Mode property to Always.

For scripts that should never execute automatically, set the Update Mode property to manual. These scripts can be run manually either from the properties dialog, or the context menu of the script as shown below.