diff --git a/code/API_definitions/number_verification.yaml b/code/API_definitions/number_verification.yaml
index 61d25e6..92664b6 100644
--- a/code/API_definitions/number_verification.yaml
+++ b/code/API_definitions/number_verification.yaml
@@ -168,6 +168,11 @@ components:
     openId:
       type: openIdConnect
       openIdConnectUrl: https://example.com/.well-known/openid-configuration
+  headers:
+    x-correlator:
+      description: Correlation id for the different services
+      schema:
+        type: string
   schemas:
     NumberVerificationRequestBody:
       type: object
@@ -228,10 +233,8 @@ components:
     Generic400:
       description: Problem with the client request
       headers:
-        X-Correlator:
-          description: Correlation id for the different services
-          schema:
-            type: string
+        x-correlator:
+          $ref: "#/components/headers/x-correlator"
       content:
         application/json:
           schema:
@@ -241,20 +244,27 @@ components:
             code: INVALID_ARGUMENT
             message: Client specified an invalid argument, request body or query param
     Generic401:
-      description: Authentication problem with the client request
+      description: Unauthorized
       headers:
-        X-Correlator:
-          description: Correlation id for the different services
-          schema:
-            type: string
+        x-correlator:
+          $ref: "#/components/headers/x-correlator"
       content:
         application/json:
           schema:
             $ref: '#/components/schemas/ErrorInfo'
-          example:
-            status: 401
-            code: UNAUTHENTICATED
-            message: Request not authenticated due to missing, invalid, or expired credentials
+          examples:
+            GENERIC_401_UNAUTHENTICATED:
+              description: Request cannot be authenticated
+              value:
+                status: 401
+                code: UNAUTHENTICATED
+                message: Request not authenticated due to missing, invalid, or expired credentials.
+            GENERIC_401_AUTHENTICATION_REQUIRED:
+              description: New authentication is needed, authentication is no longer valid
+              value:
+                status: 401
+                code: AUTHENTICATION_REQUIRED
+                message: New authentication is required.
     PhoneNumberVerificationPermissionDenied403:
       description: |
         Client does not have sufficient permission.
@@ -262,37 +272,34 @@ components:
           - Client authentication was not via mobile network. In order to check the authentication method, AMR parameter value in the 3-legged user's access token can be used and make sure that the authentication was not either by SMS+OTP nor username/password (`{"code": "NUMBER_VERIFICATION.USER_NOT_AUTHENTICATED_BY_MOBILE_NETWORK","message": "Client must authenticate via the mobile network to use this service"}`)
           - Phone number cannot be deducted from access token context.(`{"code": "NUMBER_VERIFICATION.INVALID_TOKEN_CONTEXT","message": "Phone number cannot be deducted from access token context"}`)
       headers:
-        X-Correlator:
-          description: Correlation id for the different services
-          schema:
-            type: string
+        x-correlator:
+          $ref: "#/components/headers/x-correlator"
       content:
         application/json:
           schema:
             $ref: '#/components/schemas/ErrorInfo'
           examples:
-            PermissionDenied:
+            GENERIC_403_PERMISSION_DENIED:
+              description: Permission denied. OAuth2 token access does not have the required scope or when the user fails operational security
               value:
                 status: 403
                 code: PERMISSION_DENIED
-                message: Client does not have sufficient permissions to perform this action
-            UserNotAuthenticatedByMobileNetwork:
+                message: Client does not have sufficient permissions to perform this action.
+            GENERIC_403_USER_NOT_AUTHENTICATED_BY_MOBILE_NETWORK:
               value:
                 status: 403
                 code: NUMBER_VERIFICATION.USER_NOT_AUTHENTICATED_BY_MOBILE_NETWORK
                 message: Client must authenticate via the mobile network to use this service
-            InvalidTokenContext:
+            GENERIC_403_INVALID_TOKEN_CONTEXT:
               value:
                 status: 403
-                code: NUMBER_VERIFICATION.INVALID_TOKEN_CONTEXT
+                code: INVALID_TOKEN_CONTEXT
                 message: Phone number cannot be deducted from access token context
     Generic500:
       description: Server error
       headers:
-        X-Correlator:
-          description: Correlation id for the different services
-          schema:
-            type: string
+        x-correlator:
+          $ref: "#/components/headers/x-correlator"
       content:
         application/json:
           schema:
@@ -304,10 +311,8 @@ components:
     Generic503:
       description: Service unavailable. Typically the server is down.
       headers:
-        X-Correlator:
-          description: Correlation id for the different services
-          schema:
-            type: string
+        x-correlator:
+          $ref: "#/components/headers/x-correlator"
       content:
         application/json:
           schema:
@@ -319,10 +324,8 @@ components:
     Generic504:
       description: Request time exceeded. If it happens repeatedly, consider reducing the request complexity
       headers:
-        X-Correlator:
-          description: Correlation id for the different services
-          schema:
-            type: string
+        x-correlator:
+          $ref: "#/components/headers/x-correlator"
       content:
         application/json:
           schema: