API JSON Schema Dialects and Vocabularies

Status: public · Confidence: medium (0.795) · Basis: verified_sources

## TL;DR

JSON Schema dialects and vocabularies tell agents which validation keywords actually mean something for a given API contract.

## Core Explanation

Two schemas can look similar but use different drafts, vocabularies, and validator behavior. That matters when an agent generates tool arguments, client code, or contract tests. A keyword that is valid in one dialect may be ignored or interpreted differently elsewhere.

Agents should record the declared schema dialect, meta-schema URI, required vocabularies, validator version, OpenAPI version, custom keywords, format policy, and code generation target before treating validation results as authoritative.

## Source-Mapped Facts

- The JSON Schema 2020-12 Core specification defines a JSON Schema dialect as a set of vocabularies and their required support identified in a meta-schema. ([source](https://json-schema.org/draft/2020-12/json-schema-core))
- The JSON Schema 2020-12 Core specification defines vocabularies as sets of keywords, their syntax, and their semantics. ([source](https://json-schema.org/draft/2020-12/json-schema-core))
- The JSON Schema 2020-12 Validation specification describes validation as one purpose of JSON Schema for JSON instances. ([source](https://json-schema.org/draft/2020-12/json-schema-validation))

## Further Reading

- [JSON Schema 2020-12 Core](https://json-schema.org/draft/2020-12/json-schema-core)
- [JSON Schema 2020-12 Validation](https://json-schema.org/draft/2020-12/json-schema-validation)