diff --git a/apify-api/openapi/components/schemas/actors/Version.yaml b/apify-api/openapi/components/schemas/actors/Version.yaml
index 60854403e7..ded5169247 100644
--- a/apify-api/openapi/components/schemas/actors/Version.yaml
+++ b/apify-api/openapi/components/schemas/actors/Version.yaml
@@ -26,9 +26,9 @@ properties:
     examples: [false]
     description: Whether to inject the environment variables at build time.
   buildTag:
-    type: string
+    type: [string, "null"]
     examples: [latest]
-    description: The tag name to apply to a successful build of this version.
+    description: The tag name to apply to a successful build of this version. Can be `null` when the version has no build tag.
   sourceFiles:
     $ref: ./VersionSourceFiles.yaml
     description: Applies when the `sourceType` is `SOURCE_FILES`. Represents the Actor's
diff --git a/apify-api/openapi/components/schemas/users/Plan.yaml b/apify-api/openapi/components/schemas/users/Plan.yaml
index 0e3c9bd4cb..1f9e9d1333 100644
--- a/apify-api/openapi/components/schemas/users/Plan.yaml
+++ b/apify-api/openapi/components/schemas/users/Plan.yaml
@@ -1,24 +1,9 @@
 title: Plan
+# When /users/me is accessed from an Actor run, the plan object is reduced to only
+# availableProxyGroups (see apify-core src/api/src/routes/users/user.ts). The other
+# fields are therefore only present in the full response and cannot be always required.
 required:
-  - id
-  - description
-  - isEnabled
-  - monthlyBasePriceUsd
-  - monthlyUsageCreditsUsd
-  - enabledPlatformFeatures
-  - maxMonthlyUsageUsd
-  - maxActorMemoryGbytes
-  - maxMonthlyActorComputeUnits
-  - maxMonthlyResidentialProxyGbytes
-  - maxMonthlyProxySerps
-  - maxMonthlyExternalDataTransferGbytes
-  - maxActorCount
-  - maxActorTaskCount
-  - dataRetentionDays
   - availableProxyGroups
-  - teamAccountSeatCount
-  - supportLevel
-  - availableAddOns
 type: object
 properties:
   id:
diff --git a/apify-api/openapi/components/schemas/users/UserPrivateInfo.yaml b/apify-api/openapi/components/schemas/users/UserPrivateInfo.yaml
index f0ca851990..ceca50eff3 100644
--- a/apify-api/openapi/components/schemas/users/UserPrivateInfo.yaml
+++ b/apify-api/openapi/components/schemas/users/UserPrivateInfo.yaml
@@ -1,13 +1,12 @@
 title: UserPrivateInfo
+# The id, email, profile and createdAt fields are omitted when this endpoint is accessed
+# from an Actor run, so they cannot be marked as always required (see apify-core
+# src/api/src/routes/users/user.ts REMOVE_FIELDS_WHEN_ACCESSED_BY_ACTOR_RUN).
 required:
-  - id
   - username
-  - profile
-  - email
   - proxy
   - plan
   - effectivePlatformFeatures
-  - createdAt
   - isPaying
 type: object
 properties: