openapi: 3.0.3
info:
  title: OpenMeter Billing Entitlements 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: Entitlements
  description: Metered, boolean, and static entitlements that gate access.
paths:
  /api/v1/entitlements:
    get:
      operationId: listEntitlements
      tags:
      - Entitlements
      summary: List all entitlements
      responses:
        '200':
          description: List of entitlements.
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Entitlement'
  /api/v1/entitlements/{entitlementId}:
    get:
      operationId: getEntitlementById
      tags:
      - Entitlements
      summary: Get entitlement by id
      parameters:
      - name: entitlementId
        in: path
        required: true
        schema:
          type: string
      responses:
        '200':
          description: An entitlement.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Entitlement'
  /api/v1/subjects/{subjectIdOrKey}/entitlements:
    parameters:
    - name: subjectIdOrKey
      in: path
      required: true
      schema:
        type: string
    get:
      operationId: listSubjectEntitlements
      tags:
      - Entitlements
      summary: List subject entitlements
      responses:
        '200':
          description: The subject's entitlements.
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Entitlement'
    post:
      operationId: createEntitlement
      tags:
      - Entitlements
      summary: Create a subject entitlement
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Entitlement'
      responses:
        '201':
          description: Entitlement created.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Entitlement'
  /api/v1/subjects/{subjectIdOrKey}/entitlements/{entitlementIdOrFeatureKey}/value:
    get:
      operationId: getEntitlementValue
      tags:
      - Entitlements
      summary: Get entitlement value
      description: Returns whether the subject has access and, for metered entitlements, the current balance, usage, and overage.
      parameters:
      - name: subjectIdOrKey
        in: path
        required: true
        schema:
          type: string
      - name: entitlementIdOrFeatureKey
        in: path
        required: true
        schema:
          type: string
      responses:
        '200':
          description: The entitlement value / balance.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/EntitlementValue'
components:
  schemas:
    EntitlementValue:
      type: object
      properties:
        hasAccess:
          type: boolean
        balance:
          type: number
        usage:
          type: number
        overage:
          type: number
    Entitlement:
      type: object
      required:
      - type
      - featureKey
      properties:
        id:
          type: string
        type:
          type: string
          enum:
          - metered
          - boolean
          - static
        featureKey:
          type: string
          example: api_requests
        subjectKey:
          type: string
          example: customer-1
        usagePeriod:
          type: object
          properties:
            interval:
              type: string
              enum:
              - DAY
              - WEEK
              - MONTH
              - YEAR
            anchor:
              type: string
              format: date-time
        issueAfterReset:
          type: number
          description: Amount of usage granted at the start of each usage period.
  securitySchemes:
    BearerAuth:
      type: http
      scheme: bearer
      description: OpenMeter Cloud API token supplied as a Bearer token.