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 rileyhilliard/claude-essentials --skill handling-errorsgit clone --depth 1 https://github.com/rileyhilliard/claude-essentialsWrote 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/rileyhilliard/claude-essentials/handling-errors)<a href="https://agentmods.dev/skills/rileyhilliard/claude-essentials/handling-errors"><img src="https://agentmods.dev/badge/skills/rileyhilliard/claude-essentials/handling-errors/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/rileyhilliard/claude-essentials/handling-errors"><img src="https://agentmods.dev/badge/skills/rileyhilliard/claude-essentials/handling-errors.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 | $0.00035 | $0.00560 |
| Opus 5.5 | $0.00014 | $0.00224 |
| Sonnet 5.5 | $0.00007 | $0.00112 |
| Haiku 4.5 | $0.00003 | $0.00056 |
Grade A, and why
handling-errors 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 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
try { return await fetch(url); } How it starts
The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.
If the current repo has its own rules/skills covering this topic (check .claude/rules/ and repo CLAUDE.md), those take precedence — apply this skill only where they're silent.
Handling Errors
Error Categories
| Type | Examples | Handling |
|---|---|---|
| Expected | Validation, Not found, Unauthorized | Return Result type, log info |
| Transient | Network timeout, Rate limit | Retry with backoff, log warn |
| Unexpected | Null reference, DB crash | Log error, show support ID |
| Critical | Auth down, Payment gateway offline | Circuit breaker, alert |
Fail Fast vs Degrade Gracefully
Fail fast for critical dependencies:
await connectToDatabase(); // Throws on failure - app can't run without it
Degrade gracefully for optional features:
const prefs = await loadPreferences(userId).catch(() => DEFAULT_PREFS);
Log at the Right Layer
// ❌ Logging at every layer = same error 3x
async function fetchData() {
try { return await fetch(url); }
catch (e) { console.error("Fetch failed:", e); throw e; }
}
// ✅ Log once where handled
async function fetchData() {
const response = await fetch(url);
if (!response.ok) throw new Error(`HTTP ${response.status}`);
return response;
}
// Top level logs the error once
Language-Specific Patterns
- TypeScript/React: See references/typescript-react.md for Error Boundaries, typed errors, Result pattern, UI display
- Python: See references/python.md for EAFP, exception chaining, context managers
- Go: See references/go.md for explicit error returns, wrapping with %w, sentinel errors
Anti-Patterns
| Pattern | Problem | Fix |
|---|---|---|
| Empty catch blocks | Hides errors | Log or re-throw |
return false on error |
Loses context | Return Result type |
| Generic "Error" messages | Undebuggable | Include what/why/context |
| Logging same error at each layer | Log pollution | Log once at boundary |
Bare except: / catch (e) all |
Catches system signals | Catch specific types |
What ships with it
3 files 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.
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 · 66 lines · 35 tokens per session scan A 94e1c9cbcce1
handling-errors is a skill published in the GitHub repository rileyhilliard/claude-essentials (130 stars, last pushed 2mo ago), licensed MIT. It adds 35 tokens to every session and 560 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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