```json { "classifications": [ { "column": "id", "role": "identifier", "confidence": 1.0, "reason": "Primary key with unique values for each row (10118 distinct in 10118 rows)" }, { "column": "tables_catalog_id", "role": "identifier", "confidence": 1.0, "reason": "Foreign key referencing tables_catalog; used for JOINs (508 distinct values, repeating across rows)" }, { "column": "row_index", "role": "dimension", "confidence": 0.95, "reason": "Low-cardinality numeric code (0-19) representing row position; used for grouping/filtering rather than aggregation" }, { "column": "row_json", "role": "attribute", "confidence": 1.0, "reason": "Free-form JSON text containing descriptive contact information; displayed but never grouped or aggregated" } ] } ```