Attribute names - whatever their type - are:
- Case-sensitive. 'pronoun', 'ProNoun', 'Pronoun', 'PRONOUN' are all valid names that if created would be 4 discrete attributes.
- Only upper or lower case letters an numerals are allowed in attribute names. So, allowed characters: A-Z, a-z, 0-9 (and excluding commas & hyphens!). The Create Attribute dialog for making new user attributes will suppress keyboard input for any other characters to help enforce this rule. So you may have 'ToDo' but not 'To-Do', 'To_Do' or To Do' as an attribute name. A name of '8' or '009' is allowed but probably none too useful.
Although you may use any letter case combination it is worth noting that the general style in Tinderbox - and examples in the manual etc., tend to one of two styles opening capital ('Prototype') or inter-capitalised ('AgentPriority'). For newer users, adopting the latter form for user attributes will help to distinguish attributes when seen in action and export code.
Perhaps self-evident, but adopting self explanatory names is useful both in writing codes but also when displaying key attributes.
NOTE re Attribute names & the $-prefix. In action code, when an attribute's value is referred to a $-prefix is used. Thus to call the value if the attribute WordCount, $WordCount is used. To refer to the name of said attribute, use "WordCount". Within aTbRef, inline references in general text which refer to Tinderbox attributes names generally use a $-prefix as a marker that it is an attribute name being cited. The latter is a slight variance with in-app usage but does aid clarity in the articles.