{
    "action": "tool_call",
    "reasoning": "To find duplicates or near-duplicates, I need to check for rows that repeat across key identifying columns. The most comprehensive approach is to check each major table for duplicate rows. I'll start with the largest tables (columns_catalog, job_logs, llm_calls) and look for exact duplicates by grouping on all non-metadata columns (excluding _ingestion_timestamp, _batch_id, _source_file, _source_system which are ingestion artifacts). For columns_catalog, the natural key would be tables_catalog_id + column_name + ordinal, since these should uniquely identify a column in a table.",
    "tool": "query_sql",
    "args": {
        "sql": "SELECT tables_catalog_id, column_name, ordinal, COUNT(*) as duplicate_count FROM raw.columns_catalog GROUP BY tables_catalog_id, column_name, ordinal HAVING COUNT(*) > 1 ORDER BY duplicate_count DESC LIMIT 50",
        "purpose": "Find duplicate rows in columns_catalog based on natural key (table + column + ordinal)",
        "source": "raw"
    }
}