{
    "action": "tool_call",
    "reasoning": "The question asks for the most common values and their frequencies for the main categorical columns. From the evidence, I can see that Species is the only main categorical column (role=dimension, ~3 distinct values). The metadata columns (_batch_id, _source_file, _source_system) are technical and not 'main' columns. I should query the frequency distribution of Species values. The gold table Iris_by_Species already contains this exact breakdown with row_count per species, so I'll query that first rather than computing it from raw.",
    "tool": "query_sql",
    "args": {
        "sql": "SELECT Species, row_count FROM Iris_by_Species ORDER BY row_count DESC",
        "purpose": "Get the frequency distribution of Species values from the pre-aggregated gold table",
        "source": "gold"
    }
}