{
    "action": "tool_call",
    "reasoning": "I need to compute null counts for all columns in the adsl table. I'll write a comprehensive query that aggregates null counts across all columns efficiently using COUNT(*) - COUNT(column) for each column.",
    "tool": "query_sql",
    "args": {
        "sql": "SELECT COUNT(*) as total_rows, COUNT(*) - COUNT(STUDYID) as STUDYID_nulls, COUNT(*) - COUNT(USUBJID) as USUBJID_nulls, COUNT(*) - COUNT(SUBJID) as SUBJID_nulls, COUNT(*) - COUNT(RFSTDTC) as RFSTDTC_nulls, COUNT(*) - COUNT(RFENDTC) as RFENDTC_nulls, COUNT(*) - COUNT(RFXSTDTC) as RFXSTDTC_nulls, COUNT(*) - COUNT(RFXENDTC) as RFXENDTC_nulls, COUNT(*) - COUNT(RFICDTC) as RFICDTC_nulls, COUNT(*) - COUNT(RFPENDTC) as RFPENDTC_nulls, COUNT(*) - COUNT(DTHDTC) as DTHDTC_nulls, COUNT(*) - COUNT(DTHFL) as DTHFL_nulls, COUNT(*) - COUNT(SITEID) as SITEID_nulls, COUNT(*) - COUNT(AGE) as AGE_nulls, COUNT(*) - COUNT(AGEU) as AGEU_nulls, COUNT(*) - COUNT(SEX) as SEX_nulls, COUNT(*) - COUNT(RACE) as RACE_nulls, COUNT(*) - COUNT(ETHNIC) as ETHNIC_nulls, COUNT(*) - COUNT(ARMCD) as ARMCD_nulls, COUNT(*) - COUNT(ARM) as ARM_nulls, COUNT(*) - COUNT(ACTARMCD) as ACTARMCD_nulls, COUNT(*) - COUNT(ACTARM) as ACTARM_nulls, COUNT(*) - COUNT(COUNTRY) as COUNTRY_nulls, COUNT(*) - COUNT(DMDTC) as DMDTC_nulls, COUNT(*) - COUNT(DMDY) as DMDY_nulls FROM raw.adsl",
        "purpose": "Get null counts for first 25 columns in adsl table"
    }
}