The API Designer for RAML is built by MuleSoft, and is a web-based editor designed to help you author RAML specifications for your APIs.
RAML is a human-and-machine readable modeling language for REST APIs, backed by a workgroup of industry leaders.
To learn more about the RAML specification and other tools which support RAML, please visit http://www.raml.org.
For specific questions, or to get help from the community, head to the community forum at http://forums.raml.org.