prove_it: Skill for Claude Code

.claude/skills/prove-feature/SKILL.md

prove-feature is a skill for Claude Code from searlsco/prove_it. It costs 81 tokens per session (5,829 once invoked), scanned A, original, MIT.

A method for testing a proveit feature in a temporary, realistic project from start to finish. It runs the actual feature and creates a readable session transcript showing what happened.

In plain words
What is it for?
Use it to prove a feature, reproduce a bug, or test a reviewer, task, or condition by creating focused examples and observing the real results.
Why use it?
A configuration being accepted does not prove that a feature works. This method tests both a case where the feature should act and a case where it should not.

Skill for Claude Code

Written for Claude Code: PreToolUse hook event. Also seen: reads .claude/ paths.

This is searlsco/prove_it's own configuration. It tells Claude Code how to work on prove_it itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything prove_it configures →

Reuse

Borrowing it

Nothing to install: this file belongs to searlsco/prove_it. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/searlsco/prove_it/main/.claude/skills/prove-feature/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/searlsco/prove_it

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for prove-feature

README.md
[![agentmods](https://agentmods.dev/badge/skills/searlsco/prove_it/prove-feature/github.svg)](https://agentmods.dev/skills/searlsco/prove_it/prove-feature)
Your own site
<a href="https://agentmods.dev/skills/searlsco/prove_it/prove-feature"><img src="https://agentmods.dev/badge/skills/searlsco/prove_it/prove-feature/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for prove-feature

Your own site · 80×15
<a href="https://agentmods.dev/skills/searlsco/prove_it/prove-feature"><img src="https://agentmods.dev/badge/skills/searlsco/prove_it/prove-feature.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,829 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00081 $0.05829
Opus 5.5 $0.00032 $0.02332
Sonnet 5.5 $0.00016 $0.01166
Haiku 4.5 $0.00008 $0.00583

Measured 2mo ago against content hash 7bc4bc2f25b2, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

prove-feature scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

const { spawnSync } = require('child_process')
.claude/skills/prove-feature/SKILL.md · 613 lines

How it starts

The opening of the file, as written. The whole thing — 613 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Prove a feature works (or doesn't)

Build a throwaway project and exercise a prove_it feature through the real dispatcher pipeline. The output is a human-readable transcript the user can read to confirm the system works end-to-end.

What "prove" means — read this first

Proving a feature means watching the feature do its actual job, not just watching the dispatcher accept a config and return a decision.

If the feature is a reviewer that detects dead code, you must:

  1. Create a project that contains dead code → run the reviewer → see it catch the dead code
  2. Create a project that has no dead code → run the reviewer → see it pass clean

If the feature is a task that validates API design, you must:

  1. Write an API file with real design violations → see the task reject it
  2. Write a clean API file → see the task approve it

If the feature is a when-condition gate, you must:

  1. Run with the condition unmet → see the task get skipped
  2. Run with the condition met → see the task actually execute and produce its real output

The pattern is always the same: construct a realistic situation where the feature's logic is exercised, then observe it both succeed and fail. A test that only checks "did the dispatcher return allow/deny" without verifying the feature itself inspected the right thing and made the right call is not a proof.

The critical question

Before writing any code, answer this: "What real-world situation does this feature exist to handle, and how will I simulate that situation in a throwaway project?"

If you can't answer that, you don't understand the feature well enough to prove it yet. Stop and think harder.

Anti-patterns — do NOT do these

Plumbing-only tests. Testing that the dispatcher routes to a script and returns the script's exit code is testing prove_it's plumbing, not the feature. The feature is what the script does. You must create input that makes the script's logic actually fire.

Read the full file on GitHub · 613 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2mo ago First seen · 613 lines · 81 tokens per session scan A 7bc4bc2f25b2

Subscribe to this mod's changes

prove-feature is a skill published in the GitHub repository searlsco/prove_it (200 stars, last pushed 1mo ago), licensed MIT. It adds 81 tokens to every session and 5,829 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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