# How I Use AI Prompts to Ship Free Pet-Care Calculators

> Published 2026-10-20 · https://www.promptzone.com/caninecalc/how-i-use-ai-prompts-to-ship-free-pet-care-calculators-37gb

I run a small project called CanineCalc that publishes free dog calculators and research-backed care guides — puppy weight and size estimators, calorie and feeding calculators, a crate size finder, and more.

Most of the tooling gets prototyped with a repeatable prompt workflow before I write production code. Here is the version I keep coming back to:

## 1. Spec first, code second

My opening prompt never asks for code. It asks the model to write a plain-English spec: inputs, outputs, edge cases, and the formulas the calculator needs. Reviewing that spec first catches most of the mistakes that would otherwise hide inside generated code.

## 2. Make the model state its assumptions

Pet care is full of rules of thumb that change by breed, age, and activity level. I prompt the model to list every assumption it bakes into a formula and to flag anything it is uncertain about. The flagged items become the parts I research and pin down myself, which keeps the final tool honest.

## 3. Generate the unhappy path

The most useful prompt in the sequence asks for edge cases: empty inputs, extreme values, mixed units. I keep that list next to the calculator and turn it into validation rules and test cases.

## 4. Iterate in the open

Once the calculator ships, real users find the inputs I never imagined. Each round of feedback becomes a new prompt: describe the confusing case, ask for the cleanest way to handle it, and update the tool. The loop is slow but it compounds.

One example of the result is a [free dog calorie calculator](https://caninecalc.com/dog-calorie-calculator/) — it estimates daily calories from a dog's weight and activity level, and every assumption it uses is spelled out on the page.

The takeaway: prompts are cheap and published tools are forever. Write the spec with the model, verify the assumptions yourself, and ship the calculator.