JSON Schema
JSON Schema is the standard way to document and validate API request/response shapes. OpenAPI 3.1 fully adopts it. Know it if you design APIs.
What It Defines
Vocabulary for annotating and validating JSON documents. Defines schema keywords: type, properties, required, enum, allOf, anyOf, oneOf, $ref, format, and pattern. Used in OpenAPI, AsyncAPI, and validation libraries.
Canonical (Normative)
Convenient (Practical)
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
JSON is the lingua franca of web APIs. RFC 8259 is short and worth reading once — it clarifies edge cases around numbers, encoding, and trailing commas.
OpenAPI is the de-facto standard for API documentation, code generation, mock servers, and contract testing. Most APIs you build should have an OpenAPI spec.
If you have event-driven systems (Kafka, RabbitMQ, WebSocket APIs, IoT), AsyncAPI is the description format. Analogous to OpenAPI for async what OpenAPI is for REST.