CXone Admin API: Bulk updating agent skill proficiencies via REST endpoint

We are attempting to synchronize agent skill proficiencies from our external HR system into CXone. The goal is to update the proficiency level (e.g., beginner, intermediate, expert) for a specific list of agents against a defined set of skills.

The documentation suggests using the PATCH /api/v2/agents/{agentId} endpoint, but we are looking for a way to batch these updates. We tried sending a payload to the bulk update endpoint, but it seems to reject the skill proficiency objects.

Here is the structure we are sending to /api/v2/agents/bulk-update:

{
 "agents": [
 {
 "id": "agent-123",
 "skillProficiencies": [
 {
 "skillId": "skill-456",
 "proficiency": "expert"
 },
 {
 "skillId": "skill-789",
 "proficiency": "intermediate"
 }
 ]
 }
 ]
}

The response is a 400 Bad Request with the following error:

{
 "errors": [
 {
 "message": "Invalid property 'skillProficiencies' in update payload",
 "code": "VALIDATION_ERROR"
 }
 ]
}

It appears the bulk endpoint does not support the skillProficiencies array. We have verified that a single PATCH to /api/v2/agents/{agentId} works correctly with this payload. However, making individual calls for 500+ agents is inefficient and risks hitting rate limits.

Is there a supported REST API method to bulk update skill proficiencies? Or do we need to implement a retry logic with exponential backoff for individual agent updates? We are using the Python SDK for this integration.