Create an alert

curl --request POST \
  --url https://api.getlago.com/api/v1/subscriptions/{external_id}/alerts \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "alert": {
    "code": "storage_threshold_alert",
    "billable_metric_code": "storage_usage",
    "name": "Storage Usage Alert",
    "thresholds": [
      {
        "code": "warn",
        "recurring": false,
        "value": 99
      }
    ],
    "alert_type": "billable_metric_current_usage_amount"
  }
}'

{
  "alert": {
    "lago_id": "1a901a90-1a90-1a90-1a90-1a901a901a90",
    "lago_organization_id": "1a901a90-1a90-1a90-1a90-1a901a901a90",
    "subscription_external_id": "sub_1234567890",
    "customer_external_id": "cus_0987654321",
    "billable_metric": {
      "lago_id": "1a901a90-1a90-1a90-1a90-1a901a901a90",
      "name": "Storage",
      "code": "storage",
      "description": "GB of storage used in my application",
      "recurring": false,
      "rounding_function": "round",
      "rounding_precision": 2,
      "created_at": "2022-09-14T16:35:31Z",
      "expression": "round((ended_at - started_at) * units)",
      "field_name": "gb",
      "aggregation_type": "sum_agg",
      "weighted_interval": "seconds",
      "filters": [
        {
          "key": "region",
          "values": [
            "us-east-1"
          ]
        }
      ]
    },
    "alert_type": "billable_metric_current_usage_amount",
    "code": "storage_threshold_alert",
    "name": "Storage Usage Alert",
    "previous_value": 1000,
    "last_processed_at": "2025-05-19T10:04:21Z",
    "thresholds": [
      {
        "code": "warn",
        "recurring": false,
        "value": "99.0"
      }
    ],
    "created_at": "2025-03-20T10:00:00Z"
  }
}