schema-message-type-string

Requires an error schema's message property to use type: string.

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

Intent

Error messages are human-readable text. A consistent string type keeps client rendering and logging predictable.

Flags

A message property in the first media-type schema of a 4xx or 5xx response when its type is not string. A missing type is also reported.

Does not flag

String messages, error schemas without message, and non-error responses. Use error-schema-message to require the property itself.

See it fail

responses:
  '400':
    description: Invalid request
    content:
      application/problem+json:
        schema:
          type: object
          properties:
            message:
              type: array
              items:
                type: string

Diagnostic: Error property `message` should be string.

Fix it

responses:
  '400':
    description: Invalid request
    content:
      application/problem+json:
        schema:
          type: object
          properties:
            message:
              type: string

Configure

profiles:
  default:
    rules:
      extends: [recommended]
      override:
        schema-message-type-string: error

Nearby: error-schema-message, schema-code-type-string.