OSHA specifies certain features of caged ladders, which can be found online in Code of Federal Regulations.
These specifications in turn are based on older versions of certain ANSI documents. Several years ago, OSHA issued a "proposed" updated standard based on newer versions of the ANSI documents, but it never has been officially adopted. Search through some of the OSHA interpretations for information on the issue.
In any case, OSHA specifies some details, such as width of hoops, but doesn't specify other details, such as thickness of hoops, or loads for which they are designed.
Note that ladders for certain industries, such as construction, have different standards than the "General Industry" standard.