diff --git a/apis/flags.go b/apis/flags.go
index ad48b8b..33f08bf 100644
--- a/apis/flags.go
+++ b/apis/flags.go
@@ -5,19 +5,19 @@ import (
 	"net/http"
 
 	custom_errors "github.com/cheetahbyte/flagly/internal/error"
-	"github.com/cheetahbyte/flagly/internal/evaluation"
 	"github.com/cheetahbyte/flagly/internal/utils"
 	"github.com/cheetahbyte/flagly/pkg/flagly"
 	"github.com/gin-gonic/gin"
 )
 
 type FlagAPI struct {
-	store        *flagly.Storage
-	auditService flagly.AuditService
+	store             *flagly.Storage
+	auditService      flagly.AuditService
+	evaluationService flagly.EvaluationService
 }
 
-func NewFlagAPI(store *flagly.Storage, auditService flagly.AuditService) *FlagAPI {
-	return &FlagAPI{store: store, auditService: auditService}
+func NewFlagAPI(store *flagly.Storage, auditService flagly.AuditService, evaluationService flagly.EvaluationService) *FlagAPI {
+	return &FlagAPI{store: store, auditService: auditService, evaluationService: evaluationService}
 }
 
 func (api *FlagAPI) RegisterRoutes(router *gin.RouterGroup) {
@@ -101,7 +101,7 @@ func (api *FlagAPI) PostEvaluateFlag(c *gin.Context) {
 		return
 	}
 
-	result := evaluation.EvaluateFlag(*flag, data.User, data.Environment)
+	result, _ := api.evaluationService.EvaluateFlag(*flag, data.User, data.Environment)
 
 	api.auditService.TrackEvaluation(c, *flag, data.User, data.Environment, result)
 
diff --git a/internal/audit/audit.go b/internal/audit/audit.go
index 3691955..aede87b 100644
--- a/internal/audit/audit.go
+++ b/internal/audit/audit.go
@@ -6,13 +6,9 @@ import (
 	"github.com/gin-gonic/gin"
 )
 
-type AuditService interface {
-	TrackEvaluation(c *gin.Context, flag flagly.Flag, user flagly.User, environment string, result bool)
-}
-
 type DefaultAuditService struct{}
 
-func NewDefaultAuditService() AuditService {
+func NewDefaultAuditService() flagly.AuditService {
 	return &DefaultAuditService{}
 }
 
diff --git a/internal/evaluation/evaluate.go b/internal/evaluation/evaluate.go
index 2cb79d1..5a060f4 100644
--- a/internal/evaluation/evaluate.go
+++ b/internal/evaluation/evaluate.go
@@ -7,21 +7,25 @@ import (
 	"github.com/spaolacci/murmur3"
 )
 
-// calculates the rollout percentage bucket in which the user is located.
+type DefaultEvaluationService struct{}
+
+func NewDefaultAuditService() flagly.EvaluationService {
+	return &DefaultEvaluationService{}
+}
+
 func calculateRolloutBucket(identifier string) int {
 	hash := murmur3.Sum32([]byte(identifier))
 	return int(hash % 100)
 }
 
-func EvaluateFlag(flag flagly.Flag, user flagly.User, environment string) bool {
-	// check if environment is enabled
+func (s *DefaultEvaluationService) EvaluateFlag(flag flagly.Flag, user flagly.User, environment string) (bool, error) {
 	env, ok := flag.Environments[environment]
 	if !ok {
-		return false
+		return false, nil
 	}
 	fmt.Println(env)
 	if env.Rollout.Percentage == 0 || env.Rollout.Percentage == 100 {
-		return true
+		return true, nil
 	}
 
 	// TODO: make this more dynamic
@@ -35,5 +39,5 @@ func EvaluateFlag(flag flagly.Flag, user flagly.User, environment string) bool {
 
 	// Rollout specific logic
 	hashedPercentage := calculateRolloutBucket(stickiness)
-	return env.Rollout.Percentage > hashedPercentage
+	return env.Rollout.Percentage > hashedPercentage, nil
 }
diff --git a/internal/evaluation/evaluate_test.go b/internal/evaluation/evaluate_test.go
index 48b2040..991f168 100644
--- a/internal/evaluation/evaluate_test.go
+++ b/internal/evaluation/evaluate_test.go
@@ -8,18 +8,23 @@ import (
 )
 
 func TestEvaluateFlag_UnknownEnvironment(t *testing.T) {
+	service := &DefaultEvaluationService{}
 	flag := flagly.Flag{
 		Environments: map[string]flagly.Environment{},
 	}
 	user := flagly.User{ID: "123"}
 
-	result := EvaluateFlag(flag, user, "production")
+	result, err := service.EvaluateFlag(flag, user, "production")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
 	if result {
 		t.Errorf("expected false for unknown environment, got true")
 	}
 }
 
 func TestEvaluateFlag_PercentageZero(t *testing.T) {
+	service := &DefaultEvaluationService{}
 	flag := flagly.Flag{
 		Environments: map[string]flagly.Environment{
 			"production": {
@@ -30,12 +35,17 @@ func TestEvaluateFlag_PercentageZero(t *testing.T) {
 	}
 	user := flagly.User{ID: "user1"}
 
-	if !EvaluateFlag(flag, user, "production") {
-		t.Errorf("expected true when rollout is 0%% or 100%%, got false")
+	result, err := service.EvaluateFlag(flag, user, "production")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !result {
+		t.Errorf("expected true when rollout is 0%%, got false")
 	}
 }
 
 func TestEvaluateFlag_Percentage100(t *testing.T) {
+	service := &DefaultEvaluationService{}
 	flag := flagly.Flag{
 		Environments: map[string]flagly.Environment{
 			"production": {
@@ -46,12 +56,17 @@ func TestEvaluateFlag_Percentage100(t *testing.T) {
 	}
 	user := flagly.User{ID: "user1"}
 
-	if !EvaluateFlag(flag, user, "production") {
-		t.Errorf("expected true for 100%% rollout")
+	result, err := service.EvaluateFlag(flag, user, "production")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !result {
+		t.Errorf("expected true for 100%% rollout, got false")
 	}
 }
 
 func TestEvaluateFlag_ConsistentRollout(t *testing.T) {
+	service := &DefaultEvaluationService{}
 	user := flagly.User{ID: "user42"}
 	flag := flagly.Flag{
 		Environments: map[string]flagly.Environment{
@@ -62,17 +77,21 @@ func TestEvaluateFlag_ConsistentRollout(t *testing.T) {
 		},
 	}
 
-	// Should always return the same result for the same user
-	result1 := EvaluateFlag(flag, user, "production")
-	result2 := EvaluateFlag(flag, user, "production")
+	result1, err1 := service.EvaluateFlag(flag, user, "production")
+	result2, err2 := service.EvaluateFlag(flag, user, "production")
 
+	if err1 != nil || err2 != nil {
+		t.Fatalf("unexpected error(s): %v, %v", err1, err2)
+	}
 	if result1 != result2 {
 		t.Errorf("expected consistent result for same user, got %v and %v", result1, result2)
 	}
 }
 
 func TestEvaluateFlag_WithinRollout(t *testing.T) {
-	// Find a user ID that gives a bucket under 10
+	service := &DefaultEvaluationService{}
+
+	// Find a user ID that hashes to a bucket < 10
 	var userID string
 	for i := 0; i < 10000; i++ {
 		id := "user" + strconv.Itoa(i)
@@ -81,7 +100,6 @@ func TestEvaluateFlag_WithinRollout(t *testing.T) {
 			break
 		}
 	}
-
 	if userID == "" {
 		t.Fatalf("could not find user ID with bucket < 10")
 	}
@@ -96,7 +114,11 @@ func TestEvaluateFlag_WithinRollout(t *testing.T) {
 		},
 	}
 
-	if !EvaluateFlag(flag, user, "production") {
+	result, err := service.EvaluateFlag(flag, user, "production")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if !result {
 		t.Errorf("expected true for user within rollout range")
 	}
 }
diff --git a/main.go b/main.go
index 2c409b1..dbd57b9 100644
--- a/main.go
+++ b/main.go
@@ -12,6 +12,7 @@ import (
 
 	"github.com/cheetahbyte/flagly/apis"
 	"github.com/cheetahbyte/flagly/internal/audit"
+	"github.com/cheetahbyte/flagly/internal/evaluation"
 	"github.com/cheetahbyte/flagly/internal/storage"
 	"github.com/cheetahbyte/flagly/pkg/flagly/middleware"
 	"github.com/gin-contrib/cors"
@@ -45,10 +46,11 @@ func main() {
 	router.Use(middleware.ErrorHandlerMiddleware())
 
 	auditService := audit.NewDefaultAuditService()
+	evaluationService := evaluation.NewDefaultAuditService()
 
 	apiGroup := router.Group("/api")
 	apis.NewGeneralAPI(store).RegisterRoutes(apiGroup)
-	apis.NewFlagAPI(store, auditService).RegisterRoutes(apiGroup)
+	apis.NewFlagAPI(store, auditService, evaluationService).RegisterRoutes(apiGroup)
 	apis.NewEnvironmentAPI(store).RegisterRoutes(apiGroup)
 
 	if os.Getenv("GIN_MODE") == "release" {
diff --git a/pkg/flagly/evaluation.go b/pkg/flagly/evaluation.go
new file mode 100644
index 0000000..7092ea3
--- /dev/null
+++ b/pkg/flagly/evaluation.go
@@ -0,0 +1,5 @@
+package flagly
+
+type EvaluationService interface {
+	EvaluateFlag(flag Flag, user User, environment string) (bool, error)
+}