{
  "name": "Failure messages",
  "description": "A rule's 'failureMessage' is its authored explanation for saying no. When the rule is evaluated and its condition does not pass, the message appears on the result's Failures list (rule id + message). Skipped rules - disabled, or unreached after a stop-on-first-match - report nothing: a message means the rule was actually asked.",
  "rules": [
    {
      "id": "senior-discount",
      "failureMessage": "Customer must be at least 65 for the senior discount.",
      "condition": { "field": "Customer.Age", "operator": "GreaterThanOrEqual", "value": 65 },
      "actions": [
        { "type": "setOutput", "target": "SeniorDiscount", "value": 15 }
      ]
    },
    {
      "id": "free-shipping",
      "description": "An else branch and a failureMessage work together: the else actions apply AND the failure is explained.",
      "failureMessage": "Order total is below the 200 free-shipping threshold.",
      "condition": { "field": "Order.Total", "operator": "GreaterThanOrEqual", "value": 200 },
      "actions": [
        { "type": "setOutput", "target": "Shipping", "value": 0 }
      ],
      "else": [
        { "type": "setOutput", "target": "Shipping", "value": 4.95 }
      ]
    },
    {
      "id": "adult",
      "failureMessage": "Customer must be an adult.",
      "condition": { "field": "Customer.Age", "operator": "GreaterThanOrEqual", "value": 18 },
      "actions": [
        { "type": "setOutput", "target": "Eligible", "value": true }
      ]
    }
  ]
}