diff --git a/README.md b/README.md
index 23961f6..78db969 100644
--- a/README.md
+++ b/README.md
@@ -79,7 +79,7 @@ val allPersonRules: NonEmptyList[Rule[Id, Person]] = NonEmptyList.of(
     .targetInfo("age")
     .contramap(_.age)
 )
-// allPersonRules: NonEmptyList[Rule[Id, Person]] = NonEmptyList(RuleImpl(scala.Function1$$Lambda$8362/0x0000000802349290@6b3982a9,Check UK citizenship,None,Some(citizenship)), RuleImpl(scala.Function1$$Lambda$8362/0x0000000802349290@1f4bc8ea,Check Age >= 18,None,Some(age)))
+// allPersonRules: NonEmptyList[Rule[Id, Person]] = NonEmptyList(RuleImpl(scala.Function1$$Lambda$10486/0x00000008029eb390@3b64b963,Check UK citizenship,None,Some(citizenship)), RuleImpl(scala.Function1$$Lambda$10486/0x00000008029eb390@65d4d410,Check Age >= 18,None,Some(age)))
 ```
 
 N.B. Importing even the `erules-generic` you can use macro to auto-generate the target info using `contramapTarget` method.
@@ -119,7 +119,7 @@ result.unsafeRunSync().asReport[String]
 // - Rule: Check UK citizenship
 // - Description: 
 // - Target: citizenship
-// - Execution time: 220042 nanoseconds
+// - Execution time: 123167 nanoseconds
 // 
 // - Verdict: Right(Deny)
 // - Because: Only UK citizenship is allowed!
@@ -128,7 +128,7 @@ result.unsafeRunSync().asReport[String]
 // - Rule: Check Age >= 18
 // - Description: 
 // - Target: age
-// - Execution time: 19292 nanoseconds
+// - Execution time: 16709 nanoseconds
 // 
 // - Verdict: Right(Deny)
 // - Because: Only >= 18 age are allowed!
diff --git a/core/src/main/scala/erules/core/EvalReason.scala b/core/src/main/scala/erules/core/EvalReason.scala
index 9e30a7d..782224d 100644
--- a/core/src/main/scala/erules/core/EvalReason.scala
+++ b/core/src/main/scala/erules/core/EvalReason.scala
@@ -7,7 +7,7 @@ import cats.Show
   * @param message
   *   reason message
   */
-case class EvalReason(message: String)
+case class EvalReason(message: String) extends AnyVal
 object EvalReason extends EvalReasonInstances with EvalReasonSyntax {
 
   def stringifyList(reasons: List[EvalReason]): String =
diff --git a/core/src/main/scala/erules/core/RuleResultsInterpreterVerdict.scala b/core/src/main/scala/erules/core/RuleResultsInterpreterVerdict.scala
index 3d3f741..7730902 100644
--- a/core/src/main/scala/erules/core/RuleResultsInterpreterVerdict.scala
+++ b/core/src/main/scala/erules/core/RuleResultsInterpreterVerdict.scala
@@ -5,7 +5,7 @@ import erules.core.RuleResultsInterpreterVerdict.{Allowed, Denied}
 
 /** ADT to define the possible responses of the engine evaluation.
   */
-sealed trait RuleResultsInterpreterVerdict[T] extends Serializable {
+sealed trait RuleResultsInterpreterVerdict[-T] extends Serializable {
 
   /** Result reasons
     */
diff --git a/modules/circe/README.md b/modules/circe/README.md
index fa7603a..d448d3d 100644
--- a/modules/circe/README.md
+++ b/modules/circe/README.md
@@ -53,7 +53,7 @@ val allPersonRules: NonEmptyList[Rule[Id, Person]] = NonEmptyList.of(
     .targetInfo("age")
     .contramap(_.age)
 )
-// allPersonRules: NonEmptyList[Rule[Id, Person]] = NonEmptyList(RuleImpl(scala.Function1$$Lambda$8362/0x0000000802349290@705bbf9a,Check UK citizenship,None,Some(citizenship)), RuleImpl(scala.Function1$$Lambda$8362/0x0000000802349290@1d14745f,Check Age >= 18,None,Some(age)))
+// allPersonRules: NonEmptyList[Rule[Id, Person]] = NonEmptyList(RuleImpl(scala.Function1$$Lambda$10486/0x00000008029eb390@1ea18d05,Check UK citizenship,None,Some(citizenship)), RuleImpl(scala.Function1$$Lambda$10486/0x00000008029eb390@531ca4f4,Check Age >= 18,None,Some(age)))
 ```
 
 Import 
@@ -111,13 +111,11 @@ result.unsafeRunSync().asJsonReport
 //         "verdict" : {
 //           "type" : "Deny",
 //           "reasons" : [
-//             {
-//               "message" : "Only UK citizenship is allowed!"
-//             }
+//             "Only UK citizenship is allowed!"
 //           ]
 //         },
 //         "executionTime" : {
-//           "length" : 91167,
+//           "length" : 125334,
 //           "unit" : "NANOSECONDS"
 //         }
 //       },
@@ -130,13 +128,11 @@ result.unsafeRunSync().asJsonReport
 //         "verdict" : {
 //           "type" : "Deny",
 //           "reasons" : [
-//             {
-//               "message" : "Only >= 18 age are allowed!"
-//             }
+//             "Only >= 18 age are allowed!"
 //           ]
 //         },
 //         "executionTime" : {
-//           "length" : 10750,
+//           "length" : 56500,
 //           "unit" : "NANOSECONDS"
 //         }
 //       }
diff --git a/modules/circe/src/main/scala/erules/circe/instances.scala b/modules/circe/src/main/scala/erules/circe/instances.scala
index 699097e..3f703e1 100644
--- a/modules/circe/src/main/scala/erules/circe/instances.scala
+++ b/modules/circe/src/main/scala/erules/circe/instances.scala
@@ -2,6 +2,7 @@ package erules.circe
 
 import erules.circe.report.{JsonReportInstances, JsonReportSyntax}
 import erules.core.*
+import io.circe.generic.semiauto.deriveEncoder
 
 object implicits extends CirceAllInstances with CirceAllSyntax
 
@@ -15,6 +16,9 @@ private[circe] trait BasicTypesCirceInstances {
   import io.circe.*
   import io.circe.syntax.*
 
+  implicit final val evalReasonCirceEncoder: Encoder[EvalReason] =
+    Encoder.encodeString.contramap(_.message)
+
   implicit def engineResultCirceEncoder[T: Encoder]: Encoder[EngineResult[T]] =
     io.circe.generic.semiauto.deriveEncoder[EngineResult[T]]
 
@@ -27,7 +31,7 @@ private[circe] trait BasicTypesCirceInstances {
     }
 
   implicit def ruleResultCirceEncoder[T]: Encoder[RuleResult[T, RuleVerdict]] =
-    io.circe.generic.semiauto.deriveEncoder[RuleResult[T, RuleVerdict]]
+    deriveEncoder[RuleResult[T, RuleVerdict]]
 
   implicit def ruleCirceEncoder[T]: Encoder[AnyTypedRule[T]] =
     Encoder.instance { v =>
@@ -46,9 +50,6 @@ private[circe] trait BasicTypesCirceInstances {
         "reasons" -> Json.fromValues(v.reasons.map(_.asJson))
       )
     }
-
-  implicit final val evalReasonCirceEncoder: Encoder[EvalReason] =
-    io.circe.generic.semiauto.deriveEncoder[EvalReason]
 }
 
 //---------- SYNTAX ----------
diff --git a/modules/circe/src/test/scala/erules/circe/report/JsonReportEncoderSpec.scala b/modules/circe/src/test/scala/erules/circe/report/JsonReportEncoderSpec.scala
index f86c8c2..39c072b 100644
--- a/modules/circe/src/test/scala/erules/circe/report/JsonReportEncoderSpec.scala
+++ b/modules/circe/src/test/scala/erules/circe/report/JsonReportEncoderSpec.scala
@@ -16,7 +16,7 @@ class JsonReportEncoderSpec extends munit.CatsEffectSuite {
     case class Foo(x: String, y: Int)
 
     val allowYEqZero: Rule[Id, Foo] = Rule("Check Y value").partially[Id, Foo] { case Foo(_, 0) =>
-      Allow.withoutReasons
+      Allow.because("reason")
     }
 
     val engine: IO[RulesEngineIO[Foo]] =
@@ -33,27 +33,28 @@ class JsonReportEncoderSpec extends munit.CatsEffectSuite {
       obtained = result,
       returns = json"""
           {
-            "data" : {
-              "x" : "TEST",
-              "y" : 0
-            },
-            "verdict" : {
-              "type" : "Allowed",
-              "evaluatedRules" : [
-                {
-                  "rule" : {
-                    "name" : "Check Y value",
-                    "fullDescription" : "Check Y value"
-                  },
-                  "verdict" : {
-                    "type" : "Allow",
-                    "reasons" : [
-                    ]
-                  }
-                }
-              ]
+        "data" : {
+          "x" : "TEST",
+          "y" : 0
+        },
+        "verdict" : {
+          "type" : "Allowed",
+          "evaluatedRules" : [
+            {
+              "rule" : {
+                "name" : "Check Y value",
+                "fullDescription" : "Check Y value"
+              },
+              "verdict" : {
+                "type" : "Allow",
+                "reasons" : [
+                  "reason"
+                ]
+              }
             }
-          }"""
+          ]
+        }
+      }"""
     )
   }