additionalProperties
additionalProperties is a JSON Schema keyword that controls whether object instances may contain properties not declared by the schema.
Automating API Delivery
additionalProperties is an OpenAPI schema keyword that specifies whether object properties not declared in the schema are allowed.
- How it is used
- Constrains OpenAPI object responses so undocumented properties are rejected or detected during linting, testing, or gateway validation.
- How deep it goes
- Explains strict validation, runtime checks, evolution costs, and allOf or anyOf limitations, while deferring unevaluatedProperties details.
- Examples
- Uses a product response containing undocumented numberOfReviews and reviewRating fields to demonstrate failure under a strict schema and success after schema revision.
- What you can do after
- Diagnose/debug with it by locating undocumented response fields and deciding whether to update the schema or change the API output.
Read how Automating API Delivery explains additionalProperties →
Data-Oriented Programming: Reduce software complexity
additionalProperties is a JSON Schema keyword that controls whether object properties not specified by the schema are allowed.
- How it is used
- Controls schema strictness when validating external database data and API requests or responses.
- How deep it goes
- Explains default acceptance, strict rejection with false, and request-versus-response trade-offs without covering advanced schemas.
- Examples
- Uses book database responses, dummy_property, search metadata, and a strict schema declaring additionalProperties false.
- What you can do after
- Apply it by choosing whether schemas tolerate or reject undeclared object fields at API boundaries.
Read how Data-Oriented Programming: Reduce software complexity explains additionalProperties →
Related concepts
- JSON Schemaconfigures · JSON Schema is a standard vocabulary and specification for describing, validating, and annotating the structure and constraints of JSON data.
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