content-language-response

Requires Content-Language on successful body responses that declare response headers.

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

Intent

When a response already exposes metadata through headers, declaring its content language makes text interpretation explicit.

Flags

A response whose code begins with 2, except 204, when it has both content and at least one header but no Content-Language header. Header matching is case-insensitive.

Does not flag

Responses without content, responses without any headers, 204, non-2xx responses, or responses that define Content-Language.

See it fail

responses:
  '200':
    description: OK
    headers:
      X-Trace-Id:
        schema:
          type: string
    content:
      application/json:
        schema:
          type: object

Diagnostic: Successful responses with body and headers should define `Content-Language`.

Fix it

responses:
  '200':
    description: OK
    headers:
      X-Trace-Id:
        schema:
          type: string
      Content-Language:
        schema:
          type: string
          example: en
    content:
      application/json:
        schema:
          type: object

Configure

profiles:
  default:
    rules:
      extends: [recommended]
      override:
        content-language-response: warn

Nearby: response-contains-header, content-type-response.