{
    "action": "tool_call",
    "reasoning": "I need to identify the main categorical columns first. From step-2, I can see columns with rough_kind='categorical' or semantic_role='classifier'. Let me query the column_overview metadata to find categorical columns with high row counts in their tables, then I'll query the actual data for their most common values.",
    "tool": "query_sql",
    "args": {
        "sql": "SELECT co.table_name, co.column_name, co.rough_kind, co.semantic_role, co.distinct_count, co.approx_distinct_count FROM analytics.column_overview co WHERE co.rough_kind IN ('categorical', 'text') OR co.semantic_role = 'classifier' ORDER BY co.approx_distinct_count DESC LIMIT 20",
        "purpose": "Identify main categorical columns by distinct count to determine which ones to profile for common values",
        "source": "raw"
    }
}