metaSchema

This attribute defines a URI of a JSON Schema that is the schema of the current schema.

When this attribute is defined, a validator should use the schema referenced by the value's URI (if known and available) when resolving Hyper Schema (Section 6) links (Section 6.1).

A validator may use this attribute's value to determine which version of JSON Schema the current schema is written in, and provide the appropriate validation features and behavior.

Therefore, it is recommended that all schema authors include this attribute in their schemas to prevent conflicts with future JSON Schema specification changes.

(Implementation note: $schema is instead named metaSchema internally to prevent the amount of escaping required to escape the $ character, which is normally reserved for template strings and the like.)