Excel MCP Server

Let Claude Code, Claude Desktop, Cursor or any MCP client work with your Excel files: read sheets and tables, profile columns, trace broken formulas back to the cell that caused them, and (only if you turn it on) edit with automatic backups and recalculation.

• Python 3.9+, one dependency (openpyxl). Runs locally over stdio; your files never leave your machine.
• Confined to one folder (--root): paths outside it, symlink escapes and non-Excel files are refused.
• Read-only by default. --allow-writes adds 5 editing tools.
• Works without Excel installed. LibreOffice (optional) recalculates formulas after edits.

pip install -r requirements.txt
./demo.sh            # real MCP session on the sample workbooks
./run_tests.sh       # 26 tests

Claude Code (as a plugin, or):

claude mcp add excel -- python3 /ABSOLUTE/PATH/excel-mcp-server/server.py --root ~/Spreadsheets

Claude Desktop / Cursor: copy examples/configs/claude_desktop_config.json or cursor-mcp.json and fix the paths. Add "--allow-writes" to the args to enable editing.

Options: --root DIR (or EXCEL_MCP_ROOT), --allow-writes (or EXCEL_MCP_ALLOW_WRITES=1), --max-cells 2000 per read, --no-backups, --no-recalc.

• Formula values come from the last save. openpyxl reads the value Excel stored; it can't calculate. check_formulas reports formulas that were never calculated.
• Saving with openpyxl drops every formula's stored value. After each write the server recalculates with LibreOffice when it's installed. Without it, the reply says the values are blank until you open and save the file in Excel. A test covers both paths.
• Files open in Excel are not touched. Excel's ~$ lock file blocks writes so you don't lose changes.
• Every write keeps a backup (name.bak-YYYYMMDD-HHMMSS.xlsx) next to the file, and saves go through a temp file so a crash can't leave a half-written workbook.

26 tests on Python 3.13 and 3.10 with openpyxl 3.1.5 and LibreOffice: path confinement, reading and paging, header detection, profiling, error-origin tracing on a workbook with a cascading #VALUE!, missing-sheet and #REF! formulas, every write tool, table growth, Excel lock files, recalculation with and without LibreOffice, and full JSON-RPC sessions (legacy and 2026-07-28 MCP).

• .xls (old binary format), .xlsb, .csv and password-protected files are not supported.
• Charts, pivot tables and images are kept by openpyxl only partly; don't let it edit workbooks that depend on them (read-only is fine).
• .xlsm macros are preserved on write but never run.
• Recalculation uses LibreOffice, which matches Excel for normal formulas; a few newer Excel-only functions may differ.