missing-schema-fallback

Finds places where a missing schema makes tooling fall back to an unconstrained empty schema.

Attribute	Value
Category	Schema
Maturity	Platinum
OpenAPI	Swagger 2.0; OpenAPI 3.0, 3.1, 3.2
Starter	Off
Lenient	Warning
Recommended–Complete	Error

Intent

Implicit empty schemas accept arbitrary data and hide the API's real payload shape.

Flags

• Request or response media types without schema.
• Response headers without either schema or content.
• Non-parameter array schemas without items.

Does not flag

Media types with a schema, headers with schema or content, arrays with items, and array schemas inside parameters.

See it fail

Tags:
  type: array

Diagnostic: No items schema defined for array schema defaulting to empty schema

A media type has the same problem when it declares only an example:

content:
  application/json:
    example: {status: ready}

Fix it

Describe the accepted value explicitly:

Tags:
  type: array
  items:
    type: string

For media types, add schema alongside any example.

Configure

profiles:
  default:
    rules:
      extends: [recommended]
      override:
        missing-schema-fallback: warn

Nearby: array-max-items, request-body-defined.