{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://synacl.com/protocol/v1/schemas/cmd-ack.json",
  "title": "Command acknowledgement",
  "description": "The reply to a device command (see device-cmd): on `<prefix>/devices/{deviceId}/cmd/ack` from a gateway, or `tenants/{tenantId}/devices/{deviceId}/cmd/ack` from a directly connected device. Echo the command's `correlationId` — an ack without one is rejected, and it is how the app matches the ack to the command it sent. For an actuator write, `value` is the value actually applied (digital 0|1, PWM duty 0..255, servo microseconds, …) and becomes the confirmed actuator state.",
  "type": "object",
  "required": [
    "correlationId",
    "status"
  ],
  "properties": {
    "correlationId": {
      "description": "Copied from the command being acknowledged.",
      "type": "string"
    },
    "status": {
      "type": "string",
      "enum": [
        "ok",
        "error"
      ]
    },
    "error": {
      "description": "Failure reason, or null on success.",
      "type": [
        "string",
        "null"
      ],
      "maxLength": 512
    },
    "value": {
      "description": "The applied value echoed back on actuator writes. `null` means the gateway could not read a value back (the reference firmware serialises a NaN as null); the ack is still processed, only the confirmed state is left unchanged.",
      "type": [
        "number",
        "null"
      ]
    },
    "ts": {
      "description": "Epoch milliseconds.",
      "type": "integer",
      "minimum": 0
    }
  },
  "additionalProperties": false
}