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 vSphere 6.5 REST API: "union missing required field power_state" error when listing hosts

William Lima's profile image
William Lima posted Feb 06, 2026 07:51 AM

Hello,

  I'm experiencing issues when consuming the vSphere 6.5 REST API to list ESXi hosts through the /rest/vcenter/host endpoint.

  Environment:
  - vSphere/vCenter version: 6.5
  - Problematic endpoint: GET /rest/vcenter/host (Legacy API)
  - Authentication: Session-based using vmware-api-session-id

  Error received:
  {
    "type": "com.vmware.vapi.std.errors.internal_server_error",
    "value": {
      "messages": [
        {
          "args": ["com.vmware.vcenter.host.summary", "power_state"],
          "default_message": "Structure com.vmware.vcenter.host.summary has a union that is missing a required field for this case: power_state",
          "id": "vapi.data.structure.union.missing"
        }
      ]
    }
  }

  Context:
  - All other endpoints work normally (/rest/vcenter/vm, /rest/vcenter/cluster, /rest/vcenter/datacenter)
  - Only the host endpoint returns this error
  - Error occurs on one specific vCenter server, but not on others
  - The error happens during response serialization on the vSphere server side

  Requirement:
  I only need the host ID (host) and name (name) from the ESXi hosts. I don't need the power_state field or other detailed information.

  Question:
  Is there any filter parameter or alternative endpoint in the vSphere 6.5 REST API that allows:
  1. Listing hosts without including the power_state field in the response?
  2. Getting the host list through another path (via clusters/datacenters)?
  3. Any vCenter configuration that might resolve this serialization issue?

  Any help or similar experience would be greatly appreciated!

  Thank you.