diff --git a/src/assignment-logger.spec.ts b/src/assignment-logger.spec.ts
index 88ea82c..2f4e0a9 100644
--- a/src/assignment-logger.spec.ts
+++ b/src/assignment-logger.spec.ts
@@ -1,4 +1,5 @@
 import { IAssignmentEvent } from './assignment-logger';
+import { AllocationEvaluationCode } from './flag-evaluation-details-builder';
 
 describe('IAssignmentEvent', () => {
   it('should allow adding arbitrary fields', () => {
@@ -11,6 +12,22 @@ describe('IAssignmentEvent', () => {
       timestamp: new Date().toISOString(),
       subjectAttributes: { age: 25, country: 'USA' },
       holdoutKey: 'holdout_key_123',
+      details: {
+        variationKey: 'variationKey',
+        variationValue: 'variation_123',
+        flagEvaluationCode: 'MATCH',
+        flagEvaluationDescription: '',
+        configFetchedAt: new Date().toISOString(),
+        configPublishedAt: new Date().toISOString(),
+        matchedRule: null,
+        matchedAllocation: {
+          key: 'allocation_123',
+          allocationEvaluationCode: AllocationEvaluationCode.MATCH,
+          orderPosition: 1,
+        },
+        unmatchedAllocations: [],
+        unevaluatedAllocations: [],
+      },
     };
 
     expect(event.holdoutKey).toBe('holdout_key_123');
diff --git a/src/assignment-logger.ts b/src/assignment-logger.ts
index bda5c8e..019c876 100644
--- a/src/assignment-logger.ts
+++ b/src/assignment-logger.ts
@@ -1,3 +1,5 @@
+import { IFlagEvaluationDetails } from './flag-evaluation-details-builder';
+
 export enum HoldoutVariationEnum {
   STATUS_QUO = 'status_quo',
   ALL_SHIPPED = 'all_shipped_variants',
@@ -46,6 +48,11 @@ export interface IAssignmentEvent {
   [propName: string]: unknown;
 
   metaData?: Record<string, unknown>;
+
+  /**
+   * The flag evaluation details
+   */
+  details: IFlagEvaluationDetails;
 }
 
 /**
diff --git a/src/client/eppo-client-assignment-details.spec.ts b/src/client/eppo-client-assignment-details.spec.ts
index 7c973a6..2661f7b 100644
--- a/src/client/eppo-client-assignment-details.spec.ts
+++ b/src/client/eppo-client-assignment-details.spec.ts
@@ -15,7 +15,7 @@ import FetchHttpClient from '../http-client';
 import { Flag, ObfuscatedFlag, VariationType } from '../interfaces';
 import { OperatorType } from '../rules';
 
-import EppoClient, { AssignmentDetails } from './eppo-client';
+import EppoClient, { IAssignmentDetails } from './eppo-client';
 
 async function init(configurationStore: IConfigurationStore<Flag | ObfuscatedFlag>) {
   const apiEndpoints = new ApiEndpoints({
@@ -57,7 +57,7 @@ describe('EppoClient get*AssignmentDetails', () => {
       subjectAttributes,
       0,
     );
-    const expected: AssignmentDetails<number> = {
+    const expected: IAssignmentDetails<number> = {
       value: 3,
       variationKey: 'three',
       variationValue: 3,
@@ -92,7 +92,7 @@ describe('EppoClient get*AssignmentDetails', () => {
     expect(result).toMatchObject(expected);
   });
 
-  it('should set the details for a matched split', () => {
+  it.only('should set the details for a matched split', () => {
     const client = new EppoClient(storage);
     client.setIsGracefulFailureMode(false);
     const subjectAttributes = { email: 'alice@mycompany.com', country: 'Brazil' };
@@ -102,7 +102,7 @@ describe('EppoClient get*AssignmentDetails', () => {
       subjectAttributes,
       0,
     );
-    const expected: AssignmentDetails<number> = {
+    const expected: IAssignmentDetails<number> = {
       value: 2,
       variationKey: 'two',
       variationValue: 2,
@@ -115,13 +115,13 @@ describe('EppoClient get*AssignmentDetails', () => {
       matchedAllocation: {
         key: '50/50 split',
         allocationEvaluationCode: AllocationEvaluationCode.MATCH,
-        orderPosition: 1,
+        orderPosition: 2,
       },
       unmatchedAllocations: [
         {
           key: 'targeted allocation',
           allocationEvaluationCode: AllocationEvaluationCode.FAILING_RULE,
-          orderPosition: 0,
+          orderPosition: 1,
         },
       ],
       unevaluatedAllocations: [],
@@ -139,7 +139,7 @@ describe('EppoClient get*AssignmentDetails', () => {
       subjectAttributes,
       '',
     );
-    const expected: AssignmentDetails<string> = {
+    const expected: IAssignmentDetails<string> = {
       value: 'control',
       flagEvaluationCode: 'MATCH',
       flagEvaluationDescription:
@@ -201,7 +201,7 @@ describe('EppoClient get*AssignmentDetails', () => {
       matchedAllocation: null,
       unmatchedAllocations: [],
       unevaluatedAllocations: [],
-    } as AssignmentDetails<number>);
+    } as IAssignmentDetails<number>);
   });
 
   describe('UFC General Test Cases', () => {
diff --git a/src/client/eppo-client.spec.ts b/src/client/eppo-client.spec.ts
index ca32102..0104f57 100644
--- a/src/client/eppo-client.spec.ts
+++ b/src/client/eppo-client.spec.ts
@@ -6,11 +6,9 @@ import {
   MOCK_UFC_RESPONSE_FILE,
   OBFUSCATED_MOCK_UFC_RESPONSE_FILE,
   SubjectTestCase,
-  getTestAssignmentDetails,
   getTestAssignments,
   readAssignmentTestData,
   readMockUFCResponse,
-  validateTestAssignmentDetails,
   validateTestAssignments,
 } from '../../test/testHelpers';
 import ApiEndpoints from '../api-endpoints';
@@ -19,16 +17,10 @@ import { IConfigurationStore } from '../configuration-store/configuration-store'
 import { MemoryOnlyConfigurationStore } from '../configuration-store/memory.store';
 import { MAX_EVENT_QUEUE_SIZE, POLL_INTERVAL_MS, POLL_JITTER_PCT } from '../constants';
 import FlagConfigurationRequestor from '../flag-configuration-requestor';
-import { AllocationEvaluationCode } from '../flag-evaluation-details-builder';
 import FetchHttpClient from '../http-client';
 import { Flag, ObfuscatedFlag, VariationType } from '../interfaces';
-import { OperatorType } from '../rules';
 
-import EppoClient, {
-  AssignmentDetails,
-  FlagConfigurationRequestParameters,
-  checkTypeMatch,
-} from './eppo-client';
+import EppoClient, { FlagConfigurationRequestParameters, checkTypeMatch } from './eppo-client';
 
 export async function init(configurationStore: IConfigurationStore<Flag | ObfuscatedFlag>) {
   const apiEndpoints = new ApiEndpoints({
diff --git a/src/client/eppo-client.ts b/src/client/eppo-client.ts
index 3080b21..b19c3ea 100644
--- a/src/client/eppo-client.ts
+++ b/src/client/eppo-client.ts
@@ -19,7 +19,7 @@ import { EppoValue } from '../eppo_value';
 import { Evaluator, FlagEvaluation, noneResult } from '../evaluator';
 import FlagConfigurationRequestor from '../flag-configuration-requestor';
 import {
-  FlagEvaluationDetails,
+  IFlagEvaluationDetails,
   FlagEvaluationDetailsBuilder,
 } from '../flag-evaluation-details-builder';
 import FetchHttpClient from '../http-client';
@@ -31,7 +31,7 @@ import { validateNotBlank } from '../validation';
 import { LIB_VERSION } from '../version';
 
 export interface IAssignmentDetails<T extends Variation['value'] | object>
-  extends FlagEvaluationDetails {
+  extends IFlagEvaluationDetails {
   value: T;
 }
 
@@ -400,7 +400,7 @@ export default class EppoClient {
     subjectAttributes: Record<string, AttributeType>,
     defaultValue: EppoValue,
     expectedVariationType: VariationType,
-  ): { eppoValue: EppoValue; flagEvaluationDetails: FlagEvaluationDetails } {
+  ): { eppoValue: EppoValue; flagEvaluationDetails: IFlagEvaluationDetails } {
     try {
       const result = this.getAssignmentDetail(
         flagKey,
@@ -622,6 +622,7 @@ export default class EppoClient {
         sdkLanguage: 'javascript',
         sdkLibVersion: LIB_VERSION,
       },
+      details: result.flagEvaluationDetails,
     };
 
     if (variation && allocationKey) {
diff --git a/src/evaluator.ts b/src/evaluator.ts
index cd13b86..a270120 100644
--- a/src/evaluator.ts
+++ b/src/evaluator.ts
@@ -1,7 +1,7 @@
 import {
   AllocationEvaluation,
   AllocationEvaluationCode,
-  FlagEvaluationDetails,
+  IFlagEvaluationDetails,
   FlagEvaluationDetailsBuilder,
 } from './flag-evaluation-details-builder';
 import { Flag, Shard, Range, Variation, Allocation, Split, VariationType } from './interfaces';
@@ -17,7 +17,7 @@ export interface FlagEvaluation {
   variation: Variation | null;
   extraLogging: Record<string, string>;
   doLog: boolean;
-  flagEvaluationDetails: FlagEvaluationDetails;
+  flagEvaluationDetails: IFlagEvaluationDetails;
 }
 
 export class Evaluator {
@@ -166,7 +166,7 @@ export function noneResult(
   flagKey: string,
   subjectKey: string,
   subjectAttributes: SubjectAttributes,
-  flagEvaluationDetails: FlagEvaluationDetails,
+  flagEvaluationDetails: IFlagEvaluationDetails,
 ): FlagEvaluation {
   return {
     flagKey,
diff --git a/src/flag-evaluation-details-builder.ts b/src/flag-evaluation-details-builder.ts
index 0c978df..b785dd8 100644
--- a/src/flag-evaluation-details-builder.ts
+++ b/src/flag-evaluation-details-builder.ts
@@ -26,7 +26,7 @@ export interface AllocationEvaluation {
   orderPosition: number;
 }
 
-export interface FlagEvaluationDetails {
+export interface IFlagEvaluationDetails {
   variationKey: string | null;
   variationValue: Variation['value'] | null;
   flagEvaluationCode: FlagEvaluationCode;
@@ -40,12 +40,12 @@ export interface FlagEvaluationDetails {
 }
 
 export class FlagEvaluationDetailsBuilder {
-  private variationKey: FlagEvaluationDetails['variationKey'];
-  private variationValue: FlagEvaluationDetails['variationValue'];
-  private matchedRule: FlagEvaluationDetails['matchedRule'];
-  private matchedAllocation: FlagEvaluationDetails['matchedAllocation'];
-  private unmatchedAllocations: FlagEvaluationDetails['unmatchedAllocations'];
-  private unevaluatedAllocations: FlagEvaluationDetails['unevaluatedAllocations'];
+  private variationKey: IFlagEvaluationDetails['variationKey'];
+  private variationValue: IFlagEvaluationDetails['variationValue'];
+  private matchedRule: IFlagEvaluationDetails['matchedRule'];
+  private matchedAllocation: IFlagEvaluationDetails['matchedAllocation'];
+  private unmatchedAllocations: IFlagEvaluationDetails['unmatchedAllocations'];
+  private unevaluatedAllocations: IFlagEvaluationDetails['unevaluatedAllocations'];
 
   constructor(
     private readonly allocations: Allocation[],
@@ -122,12 +122,12 @@ export class FlagEvaluationDetailsBuilder {
   buildForNoneResult = (
     flagEvaluationCode: FlagEvaluationCode,
     flagEvaluationDescription: string,
-  ): FlagEvaluationDetails => this.setNone().build(flagEvaluationCode, flagEvaluationDescription);
+  ): IFlagEvaluationDetails => this.setNone().build(flagEvaluationCode, flagEvaluationDescription);
 
   build = (
     flagEvaluationCode: FlagEvaluationCode,
     flagEvaluationDescription: string,
-  ): FlagEvaluationDetails => ({
+  ): IFlagEvaluationDetails => ({
     flagEvaluationCode,
     flagEvaluationDescription,
     variationKey: this.variationKey,
diff --git a/test/testHelpers.ts b/test/testHelpers.ts
index 7ef0c0d..b810473 100644
--- a/test/testHelpers.ts
+++ b/test/testHelpers.ts
@@ -1,6 +1,6 @@
 import * as fs from 'fs';
 
-import { AssignmentDetails } from '../src/client/eppo-client';
+import { IAssignmentDetails } from '../src/client/eppo-client';
 import { Flag, VariationType } from '../src/interfaces';
 import { AttributeType } from '../src/types';
 
@@ -13,7 +13,7 @@ export interface SubjectTestCase {
   subjectKey: string;
   subjectAttributes: Record<string, AttributeType>;
   assignment: string | number | boolean | object;
-  assignmentDetails: AssignmentDetails<string | number | boolean | object>;
+  assignmentDetails: IAssignmentDetails<string | number | boolean | object>;
 }
 
 export interface IAssignmentTestCase {
@@ -70,7 +70,7 @@ export function getTestAssignmentDetails(
   ) => never,
 ): {
   subject: SubjectTestCase;
-  assignmentDetails: AssignmentDetails<string | boolean | number | object>;
+  assignmentDetails: IAssignmentDetails<string | boolean | number | object>;
 }[] {
   return testCase.subjects.map((subject) => ({
     subject,
@@ -108,7 +108,7 @@ export function validateTestAssignments(
 export function validateTestAssignmentDetails(
   assignments: {
     subject: SubjectTestCase;
-    assignmentDetails: AssignmentDetails<string | boolean | number | object>;
+    assignmentDetails: IAssignmentDetails<string | boolean | number | object>;
   }[],
   flag: string,
 ) {