json-schema

Declare $schema as the 2020-12 dialect, set type to object, define properties with per-field constraints, list required property names as an array on the object schema, and use additionalProperties or unevaluatedProperties false to close the object.

$ref always resolves to one fixed schema chosen at authoring time, while $dynamicRef resolves through the dynamic evaluation scope so an extending schema can override the target via a matching $dynamicAnchor. Use plain $ref for ordinary recursion and $dynamicRef only for extensible base schemas.

No, format is annotation-only by default under the Format-Annotation vocabulary. It only asserts when the dialect uses the Format-Assertion vocabulary or the validator is explicitly configured to enforce formats, so check your implementation before relying on it.

Unknown or misspelled keywords are silently ignored, so a typo like require instead of required produces a schema that constrains nothing. Validate the schema itself against the 2020-12 meta-schema to catch such errors.

Use prefixItems with an array of schemas for per-index validation, and items with a single schema for elements beyond the tuple. The draft-07 style of passing an array to items and using additionalItems is not valid in 2020-12.

Use unevaluatedProperties false when composing schemas with allOf or $ref, because it sees properties evaluated across all applicators. additionalProperties false only sees the local properties and patternProperties, so it rejects properties claimed by sibling branches.