When we need to define interface, XSD Schema is best practice instead of defining Java Beans, JSON, XML, ..etc. xmlspy and Oxygen XML are costing lot of $$$. Best alternative is Eclipse XML Schema Editor. This is very user friendly.
Eclipse Editor: http://wiki.eclipse.org/index.php/Introduction_to_the_XSD_Editor
Generate XML using Eclipse and use following to get JSON data
XML to JSON Converter: http://jsontoxml.utilities-online.info/
Online JSON Validator http://jsonlint.com/
The best way to share Schema in Tree View is svg.
Use XSDVI at http://xsdvi.sourceforge.net/
Download this binary and follow the steps readme.txt file in http://xsdvi.sourceforge.net/xsdvi-20080430-1405.zip