Defining Field Help Text
You can optionally associate Help text with fields by using the <HELPTEXT> tag. Field Help text that you have assigned is displayed at run time to help users know what to enter into the field. Unlike field name and field type, field Help text is scoped to a specific work item type in a team project. This enables each team project to define its own guidelines for use of any particular field for any particular work item type. Field Help text can be up to 255 characters in length.
Note
Adding Help text can have a negative effect on the number of projects that can exist on a server. If you encounter this problem, reducing the amount of Help text could have a significant impact on the size of the metadata, which in turn helps scalability. If you need to have hundreds of projects on your Team Foundation Server, limit the use or do not use Help text in the work item type definitions (xml files).
The following example shows the assignment of Help text to the Title field.
<FIELD refname="System.Title" name="Title" type="String">
<HELPTEXT>Enter a brief description of the work item.</HELPTEXT>
</FIELD>