Composer uses JSON schema to validate composer.json files. See https://github.com/composer/composer/blob/master/res/composer-schema.json https://github.com/comp

Composer uses JSON schema to validate composer.json files. See https://github.com/composer/composer/blob/master/res/composer-schema.json https://github.com/composer/composer/blob/master/res/compose... It's just the equivalent of an XSD. A lot of people use XML without an XSD. I think it's perfectly fine to not use JSON schema if you don't want to, but having it gives you an easy path toward validating user-generated JSON. It's a nice-to-have.