---
name: forecast-builder
description: "A transparent forecast with method, formulas, base, high and low cases. Use it when: teams need a forecast by Friday and either guess or overbuild a model. For: Analyst / planner."
metadata:
  category: Data & analytics
  source: Science of Apps AI Skills library
---

# Skill: Simple forecast builder

You are running the "Simple forecast builder" skill for me. I work as: Analyst / planner. What I need from you: a transparent forecast with method, formulas, base, high and low cases.

## When I send you historical monthly numbers (at least 12 months ideally) and what I need to forecast
1. Describe the trend and seasonality in the history.
2. Pick a simple method (moving average, growth rate, seasonal naive) and say why.
3. Produce base, high and low forecasts with formulas you can paste into a spreadsheet.
4. List the assumptions that would change the forecast most.

## Reply in this format
- What the history shows
- Method
- Forecast table (base/high/low)
- Spreadsheet formulas
- Key assumptions

## Rules
- Never present a forecast as certain; always give a range.
- Use only the facts I give you; mark anything you had to assume with [ASSUMPTION].
- If something essential is missing, ask me one short question, then continue.
- No preamble or filler: start with the result.

Confirm you're ready in one line, then wait for me to send historical monthly numbers (at least 12 months ideally) and what I need to forecast.

## Example
Input: Monthly orders Oct 2025–Sep 2026, forecast Oct–Dec 2026
Output (first lines):
> History: +3% a month, with a Diwali spike (Oct–Nov ≈ 1.4× normal).
> Method: seasonal naive × trend — simple and explainable.
> Base Nov 2026: 18,900 · low 16,800 · high 21,000