Cumulocity MQTT and SmartREST API

asyncapi: 2.6.0
info:
  title: Cumulocity MQTT and SmartREST API
  version: 10.20.0
  description: |
    Constrained-device MQTT broker fronting the Cumulocity REST API with a CSV-based SmartREST 2.0 payload
    format that saves up to 80% of mobile traffic versus JSON. Supports static templates for common
    operations (s/us topic family) and tenant-defined custom templates.
  contact:
    name: Cumulocity
    url: https://cumulocity.com
servers:
  production-tls:
    url: '{tenant}.cumulocity.com:8883'
    protocol: mqtts
    description: TLS-secured MQTT 3.1.1/5.0 endpoint (recommended). 16 KiB max payload.
    variables:
      tenant:
        default: example
    security:
    - basicAuth: []
  production-plain:
    url: '{tenant}.cumulocity.com:1883'
    protocol: mqtt
    description: Plain MQTT endpoint (not recommended for production).
    variables:
      tenant:
        default: example
    security:
    - basicAuth: []
defaultContentType: text/plain
channels:
  s/us:
    description: SmartREST 2.0 static templates - device-to-cloud upstream messages (measurements, events, alarms,
      device identity, child device registration, software/firmware/configuration reporting).
    publish:
      operationId: publishSmartRestStatic
      summary: Publish a SmartREST 2.0 static-template message.
      message:
        $ref: '#/components/messages/SmartRestMessage'
  s/ds:
    description: SmartREST 2.0 static templates - cloud-to-device downstream messages (operations such as restart,
      firmware update, software update, configuration, shell command).
    subscribe:
      operationId: subscribeSmartRestStatic
      summary: Subscribe to operations delivered as SmartREST 2.0 static-template messages.
      message:
        $ref: '#/components/messages/SmartRestMessage'
  s/uc/{templateXId}:
    description: SmartREST 2.0 custom templates - device-to-cloud upstream messages using a tenant-defined template
      identified by X-ID.
    parameters:
      templateXId:
        schema: {type: string}
        description: Custom template X-ID.
    publish:
      operationId: publishSmartRestCustom
      summary: Publish a SmartREST 2.0 custom-template message.
      message:
        $ref: '#/components/messages/SmartRestMessage'
  s/dc/{templateXId}:
    description: SmartREST 2.0 custom templates - cloud-to-device downstream messages.
    parameters:
      templateXId:
        schema: {type: string}
    subscribe:
      operationId: subscribeSmartRestCustom
      summary: Subscribe to custom-template operations.
      message:
        $ref: '#/components/messages/SmartRestMessage'
  s/e:
    description: Error channel — devices subscribe to receive parse errors and operation rejection notifications.
    subscribe:
      operationId: subscribeErrors
      summary: Subscribe to error notifications.
      message:
        $ref: '#/components/messages/ErrorMessage'
components:
  messages:
    SmartRestMessage:
      name: smartRestMessage
      title: SmartREST 2.0 Message
      contentType: text/plain
      summary: A SmartREST 2.0 line — comma-separated values prefixed with a numeric template ID.
      payload:
        type: string
        examples:
        - '100,my-device-001,c8y_MQTTDevice'
        - '200,c8y_Temperature,T,21.5,C'
        - '301,c8y_Alarm,Door open,CRITICAL'
    ErrorMessage:
      name: errorMessage
      title: SmartREST Error
      contentType: text/plain
      payload:
        type: string
        examples:
        - '40,200,Invalid message format'
  securitySchemes:
    basicAuth:
      type: userPassword
      description: |
        Username in the form `{tenant}/{username}` with the user's password. The MQTT ClientId
        becomes the external ID under which the device is auto-registered.