---
name: financial-model-assumptions-documenter
description: Document the assumptions behind a financial model so it is transparent, defensible, and auditable. Use this skill whenever a user has a financial model or projection whose assumptions need writing up, wants an assumptions memo, or says 'document the model assumptions', 'explain how this model works', or 'make our projections defensible'. Trigger whenever a model's logic and drivers need to be captured so others can trust and stress-test it.
---

# Financial Model Assumptions Documenter

## What this does and why it matters
A financial model is only as trustworthy as its assumptions, and most models hide them inside formulas where no one can check them. This skill documents the assumptions, drivers, and logic behind a model in plain language, so investors, partners, and future-you can understand it, challenge it, and trust it. Undocumented models get dismissed; documented ones get funded.

## Inputs to gather
1. The model's purpose and what it projects.
2. The key drivers and the assumptions behind them (growth rates, conversion, pricing, costs, timing).
3. The basis for each assumption (historical data, benchmark, judgment).
4. The time horizon and structure.

## Method

### 1. State the purpose and structure
What the model is for and how it is built (the main sections and how they connect), so a reader can navigate it.

### 2. Document each key assumption with its basis
For every material driver: the assumption, the value, and where it comes from (actuals, market benchmark, or informed judgment). An assumption with a stated basis can be evaluated; one without is just a guess. Label judgment calls honestly.

### 3. Separate drivers from outputs
Make clear which inputs drive the model and which figures are calculated results, so a reader knows what to change to test scenarios.

### 4. Flag the sensitive assumptions
Identify the few assumptions the outcome is most sensitive to, since those deserve the most scrutiny and are where a reader should push.

### 5. Note the limitations
What the model does not account for and where it is most uncertain, stated plainly. Acknowledging limits builds credibility rather than undermining it.

## Output format
ALWAYS use:

# Model Assumptions: [Model Name]
## Purpose and structure
## Key drivers and assumptions (assumption | value | basis: actual/benchmark/judgment)
## Drivers vs calculated outputs
## Most sensitive assumptions (where the outcome hinges)
## Limitations and areas of uncertainty
## Change log note (for future updates)

## Anti-patterns to avoid
- Assumptions with no stated basis.
- Hiding judgment calls as if they were facts.
- Not distinguishing inputs from outputs.
- Claiming precision the model does not have.

## Guardrails
This documents the user's model and assumptions; it is not financial advice, a projection endorsement, or assurance the model is correct. Never invent assumptions or their basis. The user owns the accuracy of the model.

## Example
An assumptions memo documents a SaaS model's growth, churn, and CAC assumptions with each basis labeled, flags churn and conversion as the most sensitive drivers, and states plainly that the model excludes any downturn scenario.