# Prove Every Number

> Use whenever code contains a numeric constant, threshold, default, rate, capacity, tolerance, or coefficient — especially one the agent just introduced. Enforces the rule: every number is either derived (from real data or first principles, traceably) or cited (to a spec, datasheet, standard, or documented decision) — never invented, never tuned to make a test or demo pass. Real data is the truth;…

- **Type:** Skill
- **Install:** `agentstack add skill-mikestangdevs-craft-skills-prove-every-number`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [mikestangdevs](https://agentstack.voostack.com/s/mikestangdevs)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [mikestangdevs](https://github.com/mikestangdevs)
- **Source:** https://github.com/mikestangdevs/craft-skills/tree/main/skills/rigor/prove-every-number

## Install

```sh
agentstack add skill-mikestangdevs-craft-skills-prove-every-number
```

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

## About

# Prove Every Number

## The failure mode this fixes

An agent needs a value — a timeout, an efficiency factor, a retry limit, a price, a physical constant — and it *makes one up that looks plausible*. `0.95`. `30`. `1.2x`. The code runs, the demo works, and the number sits there radiating false authority. Months later someone builds a real decision on output that was quietly resting on a guess.

The malignant variant: a test fails, and instead of finding out why, the agent *adjusts the constant until it passes*. Now the codebase contains a number whose only provenance is "this made the assertion green" — a lie sticker over a defect.

This skill enforces a simple provenance rule: **every number is derived or cited.** Derived means computed from real inputs or first principles, and the derivation is traceable. Cited means it points at something outside the code's own wishes — a spec, a datasheet, a standard, an RFC, a measured benchmark, a documented product decision. A number that is neither is a finding.

## When to Use This Skill

- You (or the agent) are about to introduce a numeric literal that isn't 0, 1, or a structural index
- Reviewing AI-generated code for magic numbers and invented defaults
- A failing test was fixed by changing a constant, tolerance, or threshold
- Output feeds a real decision — money, capacity, safety, compliance, anything a customer reads
- Real input data exists but the code uses a hardcoded stand-in "for now"

**Don't use when:** the number is structurally meaningless (array index, test fixture ID, placeholder in a sketch you've labeled as a sketch). Don't demand a citation for `MAX_RETRIES = 3` in a script nobody's life depends on — scale provenance rigor to how much the output gets trusted.

## Instructions

### 1. Inventory the numbers

In the diff (or file), list every numeric literal and ask of each: *where did this come from?* Three acceptable answers: derived (show the derivation), cited (show the source), or explicitly-labeled assumption (see step 3). "It seemed reasonable" is the finding.

### 2. Prefer the real data over the stand-in

If a real input exists — a config the user provides, a measured value, an API that reports the actual number — use it, and let the constant die. The hierarchy is strict:

1. **Real data** from the actual system/site/user — the truth
2. **Derived** from real data or first principles — the calculation
3. **Cited assumption** — industry standard, spec default, published typical value, *with the source named*
4. **Invented number** — not on the list

A hardcoded value where real data was available isn't a shortcut, it's a fork from reality that every downstream result inherits.

### 3. Make assumptions loud, not embedded

When a value genuinely can't be derived or sourced yet, don't bury it in an expression. Surface it: a named constant with a comment carrying the source or the honest label (`# ASSUMED: no vendor data; typical per ; revisit`), or better, a declared default in config/schema where it's visible and overridable. The reader must be able to tell, at a glance, which numbers are load-bearing facts and which are scaffolding.

### 4. Never tune a number to pass a test

If a test fails and the fix on the table is "adjust the constant / widen the tolerance," stop. Either the code is wrong (fix the code), the test's expectation is wrong (fix it *with a justification that references reality*, not the test run), or the constant truly was wrong (then its replacement needs the same derivation-or-citation as any other number). The test result itself is never evidence for a value.

### 5. Audit sibling numbers

A made-up number rarely travels alone. When you find one, sweep the module for its siblings — the same hand that invented one default invented the others.

## Output format

```
Number provenance audit: 
Derived:  (derivations traceable)
Cited:  (sources named)
Declared assumptions: 
Findings: 
Fixes: 
```

## Anti-Patterns

| Anti-Pattern | Why it defeats the skill |
|---|---|
| Plausible-looking invention | `efficiency = 0.92` because 0.92 sounds like an efficiency. |
| Tuned to green | the constant's git history is "make test pass." |
| Buried assumption | a guess inlined into a formula, indistinguishable from a fact. |
| Stale citation | a comment citing a source the value no longer matches. A wrong citation is worse than none. |
| Citation theater | citing a source that doesn't actually contain the number. The skill is provenance, not decoration. |

## Mental Model

> Every number in the code will eventually be believed by someone who can't see where it came from. Derived or cited means they inherit evidence; invented means they inherit your guess wearing evidence's clothes.

## Source & license

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

- **Author:** [mikestangdevs](https://github.com/mikestangdevs)
- **Source:** [mikestangdevs/craft-skills](https://github.com/mikestangdevs/craft-skills)
- **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-mikestangdevs-craft-skills-prove-every-number
- Seller: https://agentstack.voostack.com/s/mikestangdevs
- Browse the marketplace: https://agentstack.voostack.com/browse

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