diff --git a/apify-api/openapi/components/schemas/webhook-dispatches/WebhookDispatchWebhookSummary.yaml b/apify-api/openapi/components/schemas/webhook-dispatches/WebhookDispatchWebhookSummary.yaml
index 4a65ed216b..7890b26fd4 100644
--- a/apify-api/openapi/components/schemas/webhook-dispatches/WebhookDispatchWebhookSummary.yaml
+++ b/apify-api/openapi/components/schemas/webhook-dispatches/WebhookDispatchWebhookSummary.yaml
@@ -8,8 +8,9 @@ properties:
   condition:
     $ref: ../webhooks/WebhookCondition.yaml
   requestUrl:
-    type: string
+    type: [string, "null"]
     format: uri
+    description: URL of the HTTP request sent by the webhook. It is `null` for hook actions other than the conventional HTTP case (e.g. Slack or email notifications).
     examples: ["https://example.com/webhook"]
   isAdHoc:
     type: boolean
diff --git a/apify-api/openapi/components/schemas/webhooks/Webhook.yaml b/apify-api/openapi/components/schemas/webhooks/Webhook.yaml
index 6ef6faf7c8..679bdd5bf1 100644
--- a/apify-api/openapi/components/schemas/webhooks/Webhook.yaml
+++ b/apify-api/openapi/components/schemas/webhooks/Webhook.yaml
@@ -7,7 +7,6 @@ required:
   - eventTypes
   - condition
   - ignoreSslErrors
-  - requestUrl
 type: object
 properties:
   id:
@@ -47,6 +46,7 @@ properties:
   requestUrl:
     type: [string, "null"]
     format: uri
+    description: URL of the HTTP request sent by the webhook. It is omitted or `null` for hook actions other than the conventional HTTP case (e.g. Slack or email notifications).
     examples: ["http://example.com/"]
   payloadTemplate:
     type: [string, "null"]
diff --git a/apify-api/openapi/paths/actor-tasks/actor-tasks@{actorTaskId}@run-sync.yaml b/apify-api/openapi/paths/actor-tasks/actor-tasks@{actorTaskId}@run-sync.yaml
index e27d4040d4..7a87b54e72 100644
--- a/apify-api/openapi/paths/actor-tasks/actor-tasks@{actorTaskId}@run-sync.yaml
+++ b/apify-api/openapi/paths/actor-tasks/actor-tasks@{actorTaskId}@run-sync.yaml
@@ -141,12 +141,16 @@ post:
       $ref: ../../components/responses/BadRequest.yaml
     "401":
       $ref: ../../components/responses/Unauthorized.yaml
+    "402":
+      $ref: ../../components/responses/PaymentRequired.yaml
     "403":
       $ref: ../../components/responses/Forbidden.yaml
     "404":
       $ref: ../../components/responses/NotFound.yaml
     "405":
       $ref: ../../components/responses/MethodNotAllowed.yaml
+    "408":
+      $ref: ../../components/responses/Timeout.yaml
     "413":
       $ref: ../../components/responses/PayloadTooLarge.yaml
     "415":