Doxygen - Generate documentation from source code
Altova XMLSpy - The XMLSpy XML Editor is a powerful tool for editing XML and related technologies. It is the only XML Editor with patented SmartFix validation, enterprise-grade editors, converters, debuggers, and code generators.
DocFX - A documentation generation tool for API reference and Markdown files!
Oxygen XML Editor - Oxygen XML Editor provides a comprehensive suite of XML authoring and development tools.
NDoc - NDoc generates class library documentation from .
Liquid Studio - XML Tools Provider: XML Studio - Graphical XML Schema Editor.