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xlsx

What it does

Reads, creates, and edits spreadsheet files — .xlsx, .xlsm, .csv, .tsv. Handles things like:

  • Adding columns, computing formulas, formatting cells
  • Cleaning up messy data (malformed rows, misplaced headers, junk values)
  • Creating charts and pivot summaries
  • Converting between tabular file formats

For data inside Google Sheets directly, use the gsheets MCP instead. This skill is for standalone files that live on disk.

When to use it

  • A client sent you a spreadsheet that needs cleanup before you can use it
  • You need to produce a deliverable that has to be an .xlsx file (not Google Sheets)
  • Tabular data lives in a .csv and needs to become a .xlsx with formulas / formatting
  • You need to convert between formats (CSV → XLSX, TSV → CSV, etc.)

How to invoke

You: clean up the spreadsheet at ~/Downloads/client-data.xlsx — the
     headers are on row 3, there are junk rows above them, and column F
     has dates in two different formats.

Claude: [reads the file, cleans it up, saves a cleaned version]

Trigger phrases:

  • "clean this spreadsheet"
  • "add a column to [file]"
  • "compute [formula] in this xlsx"
  • "convert this .csv to xlsx with formatting"

What you get back

  • A cleaned, modified, or new spreadsheet saved to disk
  • A summary of what was changed (rows cleaned, columns added, formulas applied)
  • Optionally a backup of the original (always asked first before overwriting)

Example session

You: clean up ~/Downloads/raw-creator-list.csv. Headers should be on
     row 1. Add a column for "Followers (numeric)" that parses the
     Followers column where it's currently strings like "287K" and
     "1.2M". Save as xlsx with the numeric column right-aligned.

Claude: Reading raw-creator-list.csv...
        Detected: 247 rows, 8 columns, headers on row 1 (already correct).

        Adding "Followers (numeric)" column:
        - "287K" → 287000
        - "1.2M" → 1200000
        - "456" → 456
        - 3 rows with unparseable values flagged with #N/A

        Saving as raw-creator-list-cleaned.xlsx with the new column
        right-aligned and number-formatted.

        Done. File saved.

Limitations

  • Doesn't work with Google Sheets (use gsheets MCP for that)
  • Doesn't preserve macros / VBA code if you save and reopen
  • Complex pivot tables may not round-trip cleanly through edit-and-save
  • For huge files (100K+ rows), processing slows down significantly