# Understand And Extend An Inherited Spreadsheet

> Understand existing formulas and structure then add new data while preserving the original logic. Use for tasks like “Understand and extend an inherited spreadsheet” and close variants. TEMPLATE — customize before installing.

- **Type:** Skill
- **Install:** `agentstack add skill-iankiku-agent-skill-factory-understand-and-extend-an-inherited-spreadsheet`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [iankiku](https://agentstack.voostack.com/s/iankiku)
- **Installs:** 0
- **Category:** [Data & Analytics](https://agentstack.voostack.com/c/data-and-analytics)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [iankiku](https://github.com/iankiku)
- **Source:** https://github.com/iankiku/agent-skill-factory/tree/main/templates/finance/understand-and-extend-an-inherited-spreadsheet

## Install

```sh
agentstack add skill-iankiku-agent-skill-factory-understand-and-extend-an-inherited-spreadsheet
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Understand and extend an inherited spreadsheet — skill template

Turn this template into a working skill by resolving every `TODO`. The seed prompt
below is the published Anthropic example this template was derived from; your skill
should generalize it for repeated, hands-off use.

## Outcome

Understand existing formulas and structure then add new data while preserving the original logic.

TODO: Restate the outcome for YOUR context in one sentence: who runs this, on what
input, producing what artifact, how often.

## Seed prompt (verbatim from source, © Anthropic PBC)

```text
I inherited this SaaS revenue model when Marcus left. Finance needs Q1-Q3 2026 projections by Thursday. There's a Legend tab with some basics, and a few cell comments on formulas. Can you read through those, then help me understand the rest? Specifically:

- How the four tabs connect to each other
- What the seasonality adjustment and CAC Payback formulas are actually doing
- Anything important that isn't documented

Add some visual elements so I can see the trends at a glance—data bars on the margins, or a column showing growth from baseline. And add comments explaining any complex formulas. Then extend the model through Q3 2026, following Marcus's patterns.
```

## Required context and inputs

- File creation must be enabled in settings
- Extended Thinking (recommended)
- Spreadsheet file upload required
- TODO: exact file paths / folders / message formats this skill should expect
- TODO: domain context the model cannot infer (naming conventions, thresholds, house style)

## Tools, connectors, APIs, and authentication

- No connectors detected on the source page; base Claude capabilities only
- TODO: confirm which connectors are enabled in the runtime that will execute this skill
- Authentication: connectors authenticate via their own OAuth flows — this skill must
  NEVER ask for, store, or echo credentials, tokens, or API keys. If auth is missing,
  stop and tell the user which connector to enable.

## Permissions and sensitive actions

- Reads: TODO (folders, channels, records this skill may read)
- Writes: TODO (what it may create/modify, and where)
- Held back for the primary agent / human: sending external communications, financial
  transactions, deleting or overwriting originals, submitting web forms

## Workflow

1. Describe the task
2. Give Claude context (upload spreadsheet)
3. Review what Claude creates
4. Follow up with additional prompts (changelog, variance analysis)

TODO: adapt the steps above (from the source page) into imperative instructions for the executing agent, including what to do between steps.

## Decision points

- TODO: list each point where the skill must choose between paths, with the rule to apply
- Default rule: prefer the reversible option; when two readings of the input are
  plausible, surface both rather than picking silently.

## Validation criteria

- Output matches the outcome statement above (spot-check against the seed prompt's asks)
- Every factual claim is traceable to a provided input, connector record, or cited source
- All figures reconcile to source statements/workbooks; totals recomputed programmatically, not by eye
- Flag (never silently correct) discrepancies between model and source data
- TODO: add one domain-specific check a reviewer in your org would apply

## Failure modes and fallbacks

- Ambiguous or missing input → ask one targeted question; if unattended, state the assumption inline and proceed
- Any step would take a sensitive/irreversible action → stop and hand back to the user (see Delegation)

## Delegation

Apply the repo's delegation policy (`docs/delegation-policy.md` — bundle or restate
it if you install this skill outside the repo). Defaults for this template:

- Run single-agent unless a step fans out over independent items (files, records,
  vendors, channels). Only independent work parallelizes.
- Each delegated task must ship with: the minimal context slice it needs, an explicit
  output contract, a validation check the primary agent runs on the result, and a
  fallback if it returns empty or fails.
- Final review, synthesis, and every sensitive action listed above stay with the
  primary agent.
- TODO: name the concrete subtasks (if any) that qualify for delegation here.

## Attribution

Derived from [Understand and extend an inherited spreadsheet](https://claude.com/resources/use-cases/understand-and-extend-an-inherited-spreadsheet) (retrieved 2026-07-26). Seed prompt and
workflow content © Anthropic PBC. Scaffold structure original to this repository.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [iankiku](https://github.com/iankiku)
- **Source:** [iankiku/agent-skill-factory](https://github.com/iankiku/agent-skill-factory)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-iankiku-agent-skill-factory-understand-and-extend-an-inherited-spreadsheet
- Seller: https://agentstack.voostack.com/s/iankiku
- Browse the marketplace: https://agentstack.voostack.com/browse

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