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 parhamb/design-skills --skill ux-error-handlinggit clone --depth 1 https://github.com/parhamb/design-skillsWrote 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/parhamb/design-skills/ux-error-handling)<a href="https://agentmods.dev/skills/parhamb/design-skills/ux-error-handling"><img src="https://agentmods.dev/badge/skills/parhamb/design-skills/ux-error-handling/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/parhamb/design-skills/ux-error-handling"><img src="https://agentmods.dev/badge/skills/parhamb/design-skills/ux-error-handling.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 | $0.00064 | $0.01100 |
| Opus 5 | $0.00032 | $0.00550 |
| Sonnet 5 | $0.00013 | $0.00220 |
| Haiku 4.5 | $0.00006 | $0.00110 |
Grade A, and why
ux-error-handling 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 10d 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 — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Error Handling UX
Every error is a broken promise. How you handle it determines whether the user forgives you or leaves. Good error handling is preventive, informative, and always leaves a path forward.
Checklist
| Item | Guidance |
|---|---|
| Destructive action confirmation | Single dialog. Action button is styled red. Cancel appears on the left. |
| Undo action | Snackbar with an "Undo" button for 5 to 7 seconds after deletions and moves. |
| Empty state screens | Every empty screen follows the empty-state standards below. |
| Reduce human error | Inputs are constrained, defaults are smart, and validation catches mistakes early. |
| Descriptive error messages | States what failed, why if relevant, and what the user can do next. |
| Crash recovery | App restores the previous state on relaunch after a crash. |
| Server error handling | 5xx and timeout errors show a human-readable message and a Retry button. |
Error Message Formula
[What happened] + [Why, if it helps] + [What to do next]
Examples that work:
- "We couldn't save your post. Check your connection and tap Save again."
- "Your session expired. Sign in to continue."
- "This username is already taken. Try adding numbers or a different word."
- "Payment declined. Your card ending in 4242 was not charged. [Try another card]"
Error Types and UI Patterns
| Error type | Pattern |
|---|---|
| Validation | Inline, below the field. Shown when focus leaves the field. |
| Recoverable server error | Toast or inline message with a Retry button |
| Blocking server error | Full-screen error page with Retry and Contact Support options |
| Auth error | Redirect to login. Preserve the user's intended destination. |
| Permission denied | Explain the issue and link to Settings to resolve it. |
| Network error | Top banner with offline mode fallback |
| Empty state | Positive framing with an invitation to act |
| Content not found (404) | Friendly message with suggestions and a path to Home |
| Crash | Offer to report the crash and restore the previous state |
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.
- 10d ago First seen · 127 lines · 64 tokens per session scan A 54b4c061d694
ux-error-handling is a skill published in the GitHub repository parhamb/design-skills (21 stars, last pushed 2mo ago), licensed MIT. It adds 64 tokens to every session and 1,100 once invoked, about $0.0003 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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