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 The-Artificer-of-Ciphers-LLC/skills-from-the-artificer --skill fitts-lawgit clone --depth 1 https://github.com/The-Artificer-of-Ciphers-LLC/skills-from-the-artificerWrote 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/the-artificer-of-ciphers-llc/skills-from-the-artificer/fitts-law)<a href="https://agentmods.dev/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/fitts-law"><img src="https://agentmods.dev/badge/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/fitts-law/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/the-artificer-of-ciphers-llc/skills-from-the-artificer/fitts-law"><img src="https://agentmods.dev/badge/skills/the-artificer-of-ciphers-llc/skills-from-the-artificer/fitts-law.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00110 | $0.00787 |
| Opus 5.5 | $0.00044 | $0.00315 |
| Sonnet 5.5 | $0.00022 | $0.00157 |
| Haiku 4.5 | $0.00011 | $0.00079 |
Grade A, and why
fitts-law 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 56 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Fitts's Law
"The time to acquire a target is a function of the distance to and the size of the target." — Paul Fitts, 1954
The core idea
Fitts's Law says: the time it takes to move to and click (or tap) a target depends on two things:
- Distance — how far away is the target from your starting position?
- Size — how big is the target?
Big targets that are close are fast and easy to hit. Small targets that are far away are slow and error-prone. This sounds obvious, but its implications for interface design are profound and frequently ignored.
The mathematical form: T = a + b * log2(2D/W)
Where T = time, D = distance to target, W = width of target. You don't need to use the formula — just internalize the ratio: bigger and closer is always better for targets users will interact with frequently.
Key design implications
1. The edges and corners of screens are infinitely large (on desktop). On a mouse-driven interface, the cursor stops at the screen edge. So a button in the corner is effectively infinitely large in two directions — you can fling your cursor toward it at full speed without overshooting. This is why the Mac menu bar is at the top of the screen, and why the Windows Start button is in a corner. Use screen edges for your most common actions.
2. Make interactive targets as large as reasonable. Tiny click targets — small icons, thin borders, small text links — force slow, precise movements. Buttons should be large enough to hit confidently, especially for primary actions.
3. Put frequently used controls close to where users already are. Context menus appear right at the cursor. Toolbars close to the content. Mobile keyboards auto-complete near the thumb. Distance is the enemy of speed.
4. On touch screens, finger targets need to be bigger than mouse targets. A finger is ~44px-48px in effective width; a cursor is 1px. Apple's HIG recommends touch targets of at least 44×44 points. Violating this causes frustrated tapping and missed targets.
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.
- 1mo ago First seen · 56 lines · 110 tokens per session scan A 50d5a0c1e4c3
fitts-law is a skill published in the GitHub repository The-Artificer-of-Ciphers-LLC/skills-from-the-artificer (6 stars, last pushed yesterday), licensed MIT. It adds 110 tokens to every session and 787 once invoked, about $0.0004 per session on Opus 5.5. 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 2026-08-31.
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