It will be nice to define a JavaScript function that will be called when pressing the Add, Update or Delete in the form. 
This function will

• receive the data that was introduced in the form (in a JSON)
• modify the JSON data if needed
• return true or false if the action can be performed with the error message
• the possible modified JSON will be displayed in the form if the return is false

This will allow to check some business dependent rules like the exístanse of a set of tags, list of values for certain tags, the description is not blank, restrictions on the IP depending on the hostgroups.