diff --git a/examples/03-dynamic-facts.js b/examples/03-dynamic-facts.js
index e7ddc50..58307d8 100644
--- a/examples/03-dynamic-facts.js
+++ b/examples/03-dynamic-facts.js
@@ -38,7 +38,7 @@ async function start () {
       }, {
         fact: 'account-information',
         operator: 'in',
-        value: ['active', 'paid-leave'], // 'status'' can be active or paid-leave
+        value: ['active', 'paid-leave'], // 'status' can be active or paid-leave
         path: '$.status' // access the 'status' property of "account-information"
       }, {
         fact: 'account-information',
@@ -61,18 +61,25 @@ async function start () {
    * into the engine.  The major advantage of this technique is that although there are THREE conditions
    * requiring this data, only ONE api call is made.  This results in much more efficient runtime performance.
    */
-  engine.addFact('account-information', function (params, almanac) {
-    return almanac.factValue('accountId')
-      .then(accountId => {
-        return apiClient.getAccountInformation(accountId)
-      })
+  engine.addFact('account-information', async function (params, almanac) {
+    try {
+      const accountId = await almanac.factValue('accountId')
+      return await apiClient.getAccountInformation(accountId)
+    } catch (err) {
+      console.error('Error fetching account-information:', err)
+      throw err
+    }
   })
 
   // define fact(s) known at runtime
   const facts = { accountId: 'lincoln' }
   const { events } = await engine.run(facts)
 
-  console.log(facts.accountId + ' is a ' + events.map(event => event.params.message))
+  if (events.length > 0) {
+    console.log(facts.accountId + ' is a ' + events.map(event => event.params.message).join(', '))
+  } else {
+    console.log(facts.accountId + ' did not meet conditions for the microsoft-christmas-pto rule')
+  }
 }
 start()
 
diff --git a/package.json b/package.json
index cb74404..02b1960 100644
--- a/package.json
+++ b/package.json
@@ -92,6 +92,7 @@
     "clone": "^2.1.2",
     "eventemitter2": "^6.4.4",
     "hash-it": "^6.0.0",
+    "json-rules-engine": "^7.3.1",
     "jsonpath-plus": "^10.3.0"
   }
 }
diff --git a/src/engine-default-operators.js b/src/engine-default-operators.js
index dfe33f2..3789367 100644
--- a/src/engine-default-operators.js
+++ b/src/engine-default-operators.js
@@ -3,16 +3,20 @@
 import Operator from './operator'
 
 const Operators = []
+function isCollection (value) {
+  return !!(value && (Array.isArray(value) || typeof value === 'string'))
+}
+
 Operators.push(new Operator('equal', (a, b) => a === b))
 Operators.push(new Operator('notEqual', (a, b) => a !== b))
-Operators.push(new Operator('in', (a, b) => b.indexOf(a) > -1))
-Operators.push(new Operator('notIn', (a, b) => b.indexOf(a) === -1))
+Operators.push(new Operator('in', (a, b) => isCollection(b) && b.indexOf(a) > -1))
+Operators.push(new Operator('notIn', (a, b) => !isCollection(b) || b.indexOf(a) === -1))
 
-Operators.push(new Operator('contains', (a, b) => a.indexOf(b) > -1, Array.isArray))
-Operators.push(new Operator('doesNotContain', (a, b) => a.indexOf(b) === -1, Array.isArray))
+Operators.push(new Operator('contains', (a, b) => a.indexOf(b) > -1, isCollection))
+Operators.push(new Operator('doesNotContain', (a, b) => a.indexOf(b) === -1, isCollection))
 
 function numberValidator (factValue) {
-  return Number.parseFloat(factValue).toString() !== 'NaN'
+  return typeof factValue !== 'object' && !Number.isNaN(Number.parseFloat(factValue))
 }
 Operators.push(new Operator('lessThan', (a, b) => a < b, numberValidator))
 Operators.push(new Operator('lessThanInclusive', (a, b) => a <= b, numberValidator))