Financial Modeling Agent Skill

Financial modeling

A model is an argument about how the business works, expressed in arithmetic. Its value is the

argument, not the output precision.

Structure

Three separated layers, always:

• Inputs — every assumption, in one place, each with a source and a date. An assumption buried

inside a formula is invisible and therefore never challenged.

• Calculations — no hard-coded numbers. Ever. A constant inside a formula is an untraceable

assumption.

• Outputs — the statements and the summary a decision-maker actually reads.

One row, one calculation, carried consistently across periods. Models become unauditable through

inconsistent rows more than through complexity.

Build revenue from drivers

Never grow a top-line by a percentage. Build it: volume × price, or accounts × retention ×

expansion. Driver-based models can be argued with, and being argued with is the point — a growth

rate cannot be wrong, only optimistic.

Cost structure separated into fixed, variable, and step-fixed. The step-fixed items are where plans

break, because they move in jumps nobody modeled.

Sensitivities are the deliverable

A single-scenario model tells you nothing about risk. For every model, produce:

• Which two or three assumptions actually move the answer. Usually far fewer than expected.
• Breakeven on each — how wrong can this be before the decision reverses?
• Downside case — not a haircut on the base case, but a coherent story where things go badly.

If a plan only works in the base case, that is the finding.

Presenting

Lead with the answer, then the two assumptions it rests on most heavily, then what would change it.

Never present a model without stating what it is most sensitive to — the recipient will assume

robustness you did not claim.

Never

• Report a number to more precision than the assumptions support. Five significant figures from a

guessed growth rate is false confidence.

• Build a model whose logic you cannot explain in three sentences.
• Change an assumption to reach a desired output without labeling it as a target case.