Why use JSON Schema instead of XYZ (Other) Schema Validator?

[nelsonic]

Why Not XYZ (Alternative) Schema...?

We attempted to use several "alternatives":

• schema.org - uses micro-formats or HTML "hypermedia"
  instead of a more "efficient" data format.
• GraphQL Schema - GraphQL
  is really promising. We used GraphQL
  for our "Inspirational Search" project and felt the pros & cons.
  It was good for succinctness, however the schema validation and error debugging (when something is wrong) was tedious.
  We would often spend hours trying to debug a complex schema without any luck,
  and then someone would spot a missing character
  (which was not reported in the error message) and it would "magically" work.
• Joi - superb for backend (node.js)
  validation, concise syntax, however not easy to modularize or extend.
• XSD (XML Schema Definition) - powerful but way more than what we need and
  xml is not ideal for "full-stack" where JSON can be loaded as a
  static file in Clients and easily used for client-side validation.