{
    "action": "tool_call",
    "reasoning": "I will query the column overview metadata to render a table of columns, their data types, and semantic roles. I will then explain what the columns mean in prose.",
    "tool": "query_sql",
    "args": {
        "purpose": "List columns and their data types",
        "source": "raw",
        "sql": "SELECT table_name, column_name, phys_type AS data_type, semantic_role FROM analytics.column_overview WHERE column_name NOT LIKE '\\_%' ORDER BY table_name, column_name;"
    }
}