# Create Entity Type Relations

Define schema-level relation types (e.g. reader, owner, parent) and which entity types can be subjects.

Endpoint: POST /resources/entity-types/v1/{key}/relations
Version: 1.0
Security: bearer

## Request fields (application/json):

  - `relations` (array, required)

  - `relations.key` (string, required)
    Example: "reader"

  - `relations.subjectEntityKeys` (array, required)
    Example: ["copywriter","customer"]

## Response 201 fields (application/json):

  - `vendorId` (string, required)
    Example: "123e4567-e89b-12d3-a456-426614174000"

  - `targetEntityTypeKey` (string, required)
    Example: "book"

  - `key` (string, required)
    Example: "reader"

  - `subjectEntityTypeKeys` (array, required)
    Example: ["copywriter","customer"]