openapi: 3.0.3
info:
  title: OpenMeter Billing Subjects API
  description: OpenMeter is open-source usage metering and billing for AI and API products. Ingest usage as CloudEvents, define meters that aggregate those events, query usage, manage subjects and customers, gate access with entitlements (metered, boolean, and static), features and grants, react to usage with notifications, and drive billing, plans, and subscriptions with Stripe integration. This is a faithful, representative subset of the real OpenMeter Cloud API (https://openmeter.cloud/api/v1) for API Evangelist catalog purposes; see the canonical spec at https://github.com/openmeterio/openmeter for the full surface.
  termsOfService: https://openmeter.io/terms
  contact:
    name: OpenMeter Support
    url: https://openmeter.io
    email: support@openmeter.io
  license:
    name: Apache 2.0
    url: https://www.apache.org/licenses/LICENSE-2.0
  version: 1.0.0
servers:
- url: https://openmeter.cloud
  description: OpenMeter Cloud
- url: http://localhost:8888
  description: Self-hosted (open source, default)
security:
- BearerAuth: []
tags:
- name: Subjects
  description: Subjects that usage is metered against.
paths:
  /api/v1/subjects:
    get:
      operationId: listSubjects
      tags:
      - Subjects
      summary: List subjects
      responses:
        '200':
          description: List of subjects.
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Subject'
    post:
      operationId: upsertSubject
      tags:
      - Subjects
      summary: Upsert subjects
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: array
              items:
                $ref: '#/components/schemas/Subject'
      responses:
        '200':
          description: Subjects upserted.
  /api/v1/subjects/{subjectIdOrKey}:
    parameters:
    - name: subjectIdOrKey
      in: path
      required: true
      schema:
        type: string
    get:
      operationId: getSubject
      tags:
      - Subjects
      summary: Get subject
      responses:
        '200':
          description: A subject.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Subject'
    delete:
      operationId: deleteSubject
      tags:
      - Subjects
      summary: Delete subject
      responses:
        '204':
          description: Subject deleted.
components:
  schemas:
    Subject:
      type: object
      required:
      - key
      properties:
        id:
          type: string
        key:
          type: string
          description: Unique subject key that events reference in their subject field.
          example: customer-1
        displayName:
          type: string
        metadata:
          type: object
          additionalProperties: true
        stripeCustomerId:
          type: string
          nullable: true
  securitySchemes:
    BearerAuth:
      type: http
      scheme: bearer
      description: OpenMeter Cloud API token supplied as a Bearer token.