JSON Schema for reliable API contracts
A schema workflow that treats successful and failing payloads as executable documentation rather than relying on one ideal sample.
JSON syntax only proves that a document can be parsed. A useful API contract must describe which structures and values consumers may safely expect.
Model absence and null explicitly
Required, optional, and nullable are different states. Define types, array items, enums, formats, bounds, and additionalProperties according to actual compatibility rules.
Test failures as well as success
Keep examples for missing fields, wrong types, nulls, unknown enum values, extra properties, empty arrays, and every oneOf or anyOf branch.
Manage contract evolution
Compare schemas and real payloads during releases, distinguish additive from breaking changes, and generate client types only as a reviewed starting point.
API schema checklist
- Define required optional and nullable fields
- Constrain arrays enums and formats deliberately
- Add representative invalid examples
- Review oneOf and anyOf overlap
- Test schema changes against real payloads
Related guides
Learn the workflow behind this tool and what to check next.
How to debug an API JSON response step by step
A repeatable workflow for separating transport errors, JSON syntax problems, and data-contract failures in API responses.
How to debug JSON API payloads
A practical workflow for formatting JSON, finding syntax errors, validating payload shape, and checking response status when API data looks wrong.