{
    "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 analytics.column_overview to find categorical columns with their distinct counts, then I'll query the top values for the most important ones.",
    "tool": "query_sql",
    "args": {
        "sql": "SELECT table_name, column_name, phys_type, semantic_role, rough_kind, distinct_count, approx_distinct_count FROM analytics.column_overview WHERE rough_kind = 'categorical' OR semantic_role = 'classifier' ORDER BY COALESCE(distinct_count, approx_distinct_count, 0) DESC LIMIT 30",
        "purpose": "Identify main categorical columns by distinct count to determine which ones to profile for top values",
        "source": "raw"
    }
}