Check Google Vertex Health

{
    "provider": "google-vertex",
    "health_status": "healthy",
    "status": "healthy",
    "diagnosis": {
        "credentials_available": true,
        "credential_source": "env_json",
        "project_id": "my-project",
        "location": "us-central1",
        "token_available": true,
        "token_valid": true,
        "error": null,
        "steps": [...]
    },
    "timestamp": "2025-01-01T12:00:00Z"
}