toy

toy is a skill for Claude Code from saadshahd/moo.md. It costs 34 tokens per session (484 once invoked), scanned A, original, MIT.

A small interactive environment for learning how a system behaves by operating it yourself, with visible state and step-by-step changes.

In plain words
What is it for?
Use it to make debuggers, visualizers, simulators, steppers, playgrounds, or command centers for exploring execution, migrations, data structures, algorithms, or parameters.
Why use it?
It builds intuition by showing hidden intermediate effects as you act, rather than relying only on reading explanations.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the hold plugin — 4 skills shipped together

Good fit Use it to make debuggers, visualizers, simulators, steppers, playgrounds, or command centers for exploring execution, migrations, data structures, algorithms, or parameters.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/saadshahd/moo.md/toy
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add saadshahd/moo.md --skill toy
Clone the repo
git clone --depth 1 https://github.com/saadshahd/moo.md

Made for: Claude Code.

Or install hold, the plugin that ships this one along with the rest of its 4 skills.

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 toy

README.md
[![agentmods](https://agentmods.dev/badge/skills/saadshahd/moo.md/toy/github.svg)](https://agentmods.dev/skills/saadshahd/moo.md/toy)
Your own site
<a href="https://agentmods.dev/skills/saadshahd/moo.md/toy"><img src="https://agentmods.dev/badge/skills/saadshahd/moo.md/toy/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 toy

Your own site · 80×15
<a href="https://agentmods.dev/skills/saadshahd/moo.md/toy"><img src="https://agentmods.dev/badge/skills/saadshahd/moo.md/toy.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 484 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00034 $0.00484
Opus 5 $0.00017 $0.00242
Sonnet 5 $0.00007 $0.00097
Haiku 4.5 $0.00003 $0.00048

Measured yesterday against content hash 0a3ebbc3ea9a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

toy scanned grade A with 0 findings 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 yesterday.

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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

hold/skills/toy/SKILL.md · 22 lines

What it actually says

Build the world; the human drives it. Never automate the step they are trying to learn. One behavior per world; cut every control and readout no prediction needs. Drive the real system when it is cheap to run, toy data when it is heavy. A dynamic the system does not show is labeled approximate on screen, never drawn as real.

The world shows what is hidden — the stack, the queue, the cursor, the intermediate value — at every step, scrubbable forward and back, each effect re-rendered beside its cause on every press. Room beside any step to pin a note.

Beside each control that steps or fires, room to say what it will do before pressing; the world sets the prediction beside what happened. The human reads the match; the world never scores it. A miss names the next thing to drive.

The human lacks Build A case that fixes it
How execution unfolds Stepper: scrub through time, internals visible at each step a regex engine on one input: cursor and backtrack stack at every step
What a migration, port, or bulk change does Command center: the human fires each step, before and after side by side a rename over forty files: one file per press, its before and after together
How a structure or algorithm behaves Objects they can move, values live a B-tree: drag a key in, watch the split
What a parameter or design space does Sliders with instant re-render a rate limiter: bucket size and refill rate, the traffic curve redraws on every nudge

Default medium: one page outside the repo, YYYY-MM-DD-<slug>.html, opened for them (open <path>). Then step out. Held is when their predictions land — theirs to report, not yours to claim. Say what the world leaves approximate.

The reader lacks what it is, not how it behaves → use grasp skill. The world is a playground, demo, or UI → not toy; say so and stop.

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. yesterday Changed · -4 lines · -41 tokens per session 0a3ebbc3ea9a
  2. 9d ago First seen · 26 lines · 75 tokens per session scan A eb734e46949e

Subscribe to this mod's changes

toy is a skill published in the GitHub repository saadshahd/moo.md (34 stars, last pushed 2d ago), licensed MIT. It adds 34 tokens to every session and 484 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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