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.
npx skills add SummerEngine/summer-engine-agent --skill design-mechanicgit clone --depth 1 https://github.com/SummerEngine/summer-engine-agentWrote 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.
[](https://agentmods.dev/skills/summerengine/summer-engine-agent/design-mechanic)<a href="https://agentmods.dev/skills/summerengine/summer-engine-agent/design-mechanic"><img src="https://agentmods.dev/badge/skills/summerengine/summer-engine-agent/design-mechanic/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.
<a href="https://agentmods.dev/skills/summerengine/summer-engine-agent/design-mechanic"><img src="https://agentmods.dev/badge/skills/summerengine/summer-engine-agent/design-mechanic.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00083 | $0.03070 |
| Opus 5 | $0.00042 | $0.01535 |
| Sonnet 5 | $0.00017 | $0.00614 |
| Haiku 4.5 | $0.00008 | $0.00307 |
Grade A, and why
design-mechanic 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 12d 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.
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.
Copies of this mod
1 near-identical copy found in the catalogue:
- design-mechanic — 86% identical, 56 lines differ
How it starts
The opening of the file, as written. The whole thing — 274 lines — stays where its author put it; the contents beside it link to each section on GitHub.
/design-mechanic — Design One Mechanic in Detail
Overview
A "mechanic" is a verb the player performs that produces a meaningful response from the world. Not a system. Not a feature. A verb with feedback. This skill walks the five layers of a real mechanic: input → response → feedback → failure modes → depth — then drops a node-graph sketch + GDScript stub into the project so the next session can implement it.
Core principle: a mechanic is only as good as its weakest feedback layer. A perfect parry with no audio cue is broken. A great audio cue with floaty input is broken. Walk all five layers before scaffolding.
Steps
1. Pin which mechanic
Ask exactly one question and wait:
Which mechanic? (e.g., "double-jump", "parry", "stamina-dash", "pickup", "lock-on", "crafting-recipe-craft").
If the user gives a system name ("inventory", "combat"), push back:
Inventory is a system, not a mechanic. The mechanics inside it are: pickup, equip, drop, use, swap. Which one?
2. Read context if available
If .summer/GameSoul.md exists, read it. The mechanic should fit the game brief, not exist in isolation.
Read .summer/GameSoul.md
Quote the relevant constraint back at the user:
Brief says core loop is "see obstacle, attempt, fail, learn, retry". A double-jump only matters if it changes which obstacles are reachable. Confirm that's what we're solving.
3. Walk the five layers — one at a time
Layer 1: Input. Exactly what does the player press, hold, release, time?
State a candidate, ask for refinement:
Input candidate: tap Space mid-air. Or: hold-and-release for variable height? Or: requires direction + Space? Pick one.
Layer 2: Response. What changes in the world the moment the input fires?
State the deltas. For double-jump:
Response: vertical velocity set to (jump_velocity * 0.85).
_can_double_jumpflag flips false. Visual rig plays "jump_2" anim. Audio cue. Particle burst at feet.
Layer 3: Feedback — and this is where most amateur designs collapse. Three sub-channels, all required:
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.
- 12d ago First seen · 274 lines · 83 tokens per session scan A 3fa1ee0daffa
design-mechanic is a skill published in the GitHub repository SummerEngine/summer-engine-agent (59 stars, last pushed yesterday), licensed MIT. It adds 83 tokens to every session and 3,070 once invoked, about $0.0004 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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