excel

A stateful, formula-aware Excel engine an agent can actually drive - not a file it has to parse by hand. Opens existing .xlsx/.xlsm/.xls workbooks (or creates new ones) entirely in memory, then queries and richly edits them across a whole session without reloading: cell values, typed formulas, styling, conditional formatting, data validation, charts, sheet structure and outline grouping, rows and columns, tables, and named ranges - flushed to disk with an atomic, corruption-safe save. Its standout capability is headless recalculation: Apache POI evaluates ~280 Excel functions in place, so the agent works with real computed results instead of the stale cached zeros that code-based approaches (openpyxl/pandas, or Claude's built-in spreadsheet handling) leave behind - and every read distinguishes a genuine value from an as-yet-uncomputed formula. It can also review a model, not just write one: workbook.audit scans for hardcoded constants and hidden rows, and cell.trace walks precedents and dependents. Because all edits flow through one POI writer, it never triggers the 'Excel repaired records' corruption that second-writer libraries cause. 41 tools across workbook lifecycle (incl. audit), range I/O (incl. cell styling, conditional formats, data validation, and formula tracing), sheet management, presentation and outlining, line and bar charts, tables, named ranges, and read-only VBA extraction.