sheets-modelling

A Claude Code plugin for building, auditing, and restructuring Google Sheets models that look defensible — not amateur.

Current version: 2.0.0

What's in it

Two skills, one plugin.

google-sheets-modelling — the core

Applies to every Google Sheet interaction: building, cleaning, formatting, auditing.

• Three-pass build workflow — Content → Format (mandatory phase, not polish) → Verify (post-write sanity gate)
• FAST Standard workbook structure (About / Inputs / Data / Calcs / Outputs / Checks / Disclaimer / Claude_Log) with the corkscrew-consistency rule
• Tidy data (Wickham) for Data tabs; long-format for time series
• Classic WSO colour convention — blue #0000FF for hardcoded inputs, black for formulas, green #006100 for cross-sheet refs, red #C00000 for external
• Number format spec — explicit patterns per data class (£, £m, £bn, %, multiples, counts, ratios, dates), one unit per tab
• Column-width + frozen-panes defaults — pad 20 / label 260 / sub-label 180 / year 95 / notes 160
• Pre-write discipline — range + shape declaration, ref-map of named-range targets, safe_mode: true on uncertain writes, re-read inputs after writing
• Magic-number lint — regex scan to catch hardcoded literals in formulas
• Post-write sanity gate — sector-calibrated order-of-magnitude bands, directional signs, bridge ties, no-magic-numbers-remaining
• Sign-convention assertion — memo cell + Checks row catches P&L sign flips
• Volatile-function avoidance — TODAY(), INDIRECT(), IMPORTRANGE() patterns and their fixes
• Google Sheets limits — 10M hard cap, ~1.2M practical slowdown, 60 API req/min
• Audit-first workflow — read the existing structure, report findings, wait for explicit approval before any write
• Mandatory enable_claude_log before every write tool on the paired Google Sheets MCP

financial-modelling-extras — for valuation + M&A models

Triggers on DCF / valuation / M&A / synergies / football-field / pro-forma keywords.

• DCF template — explicit FCF build, Gordon TV with FCF_{N+1} + discount-to-today, exit-multiple TV cross-check
• Football-field layout — max 4 methods, low/mid/high with source cells, no average-of-mids
• M&A pro-forma bridge — mandatory Checks row: pro_forma_ebitda == sum_of_parts
• Synergy structure — revenue vs cost split, 5-year ramp (25/65/100/100/100), revenue_synergy_flowthrough = 80%, integration cost below-the-line
• Paid vs captured synergies — standalone EV is what the seller gets; synergy PV is a buyer-side memo, never folded into EV
• Sector order-of-magnitude bands — EV/Rev, EV/EBITDA, synergy-PV-as-%-deal-EV

Install (local)

From a Claude Code session:

/plugin marketplace add /Users/matt/Claude Code Projects/sheets-modelling-plugin
/plugin install sheets-modelling@sheets-modelling-local

Restart the session. Both skills auto-trigger by their descriptions.

Upgrade from v1

/plugin update sheets-modelling

Pairs with

The Google Sheets MCP server (v0.4.0, 34 tools). The skill's formatting phase depends on MCP v2 tools: set_column_width, set_frozen, set_conditional_format, format_ranges_batch, set_data_validation, set_sheet_protection, merge_cells, plus write-tool flags (safe_mode, return_computed, ROW_COUNT_MISMATCH with suggested_range).

Iterate

• Edit skills/<skill-name>/SKILL.md
• Bump version in both .claude-plugin/plugin.json and .claude-plugin/marketplace.json
• Log the change in CHANGELOG.md
• git tag vX.Y.Z
• /plugin update sheets-modelling in Claude Code to pick up the new version

See CHANGELOG.md for version history.