Borrowing it
Nothing to install: this file belongs to j5ik2o/event-store-adapter-js. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/j5ik2o/event-store-adapter-js/main/.agents/skills/error-handling/SKILL.mdgit clone --depth 1 https://github.com/j5ik2o/event-store-adapter-jsWrote 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/j5ik2o/event-store-adapter-js/error-handling)<a href="https://agentmods.dev/skills/j5ik2o/event-store-adapter-js/error-handling"><img src="https://agentmods.dev/badge/skills/j5ik2o/event-store-adapter-js/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/j5ik2o/event-store-adapter-js/error-handling"><img src="https://agentmods.dev/badge/skills/j5ik2o/event-store-adapter-js/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 | $0.00174 | $0.01112 |
| Opus 5 | $0.00087 | $0.00556 |
| Sonnet 5 | $0.00035 | $0.00222 |
| Haiku 4.5 | $0.00017 | $0.00111 |
Grade A, and why
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 7d 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.
This is a copy
100% identical to error-handling — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 94 lines — stays where its author put it; the contents beside it link to each section on GitHub.
エラーハンドリング
回復可能性を基準にしたエラーハンドリング設計を支援する。
基本方針
ドメインロジック（ビジネスルール）では Either/Result 型を採用する。
- ドメイン層のエラーは呼び出し元が判断すべき → 型で明示
- 例外は制御フローではなく、本当の異常事態に限定
- 戻り値の型を見るだけでエラーの可能性が分かる設計
判断フロー
エラー発生
↓
回復可能か？
├─ YES → Either/Result型で表現
└─ NO → 例外/panicで即座に停止
| 回復可能 | 回復不能 |
|---|---|
| ビジネスルール違反 | 引数の不正 (IllegalArgumentException) |
| 外部システムエラー | 状態の矛盾 (IllegalStateException) |
| 権限不足・リソース競合 | 到達不可コード (unreachable) |
回復可能なエラー
Either/Result型で表現し、呼び出し元に判断を委ねる。
// TypeScript - neverthrow
function findUser(id: string): Result<User, UserError> {
if (!isValidId(id)) return err({ type: 'VALIDATION_FAILED', field: 'id' });
return repository.find(id)
? ok(user)
: err({ type: 'NOT_FOUND', userId: id });
}
回復不能なエラー
プログラムの前提条件違反は即座に停止。
// 引数の不正 → IllegalArgumentException 相当
if (order === null) throw new Error('order must not be null');
// 状態の矛盾 → IllegalStateException 相当
if (order.status === 'COMPLETED' && order.items.isEmpty())
throw new Error('completed order must have items');
// 到達不可コード → unreachable
default: throw new Error(`unreachable: ${status}`);
推奨ライブラリ
| 言語 | ライブラリ | 選択基準 |
|---|---|---|
| TypeScript | neverthrow |
Result のみで十分な場合（軽量・シンプル） |
| TypeScript | fp-ts |
関数型全般を使う場合（Option, Task, IO, Reader 等） |
| JavaScript | neverthrow |
TypeScript と同様 |
| Rust | 標準 Result<T, E> |
常にこれを使用。エラー定義には thiserror |
| Go | 標準 (T, error) |
Go らしいシンプルなコードを書く場合 |
| Go | samber/mo |
Result/Either でチェーン処理したい場合 |
| Scala | 標準 Either[L, R] |
標準で十分。cats は大規模 FP 向け |
| Java | vavr.io Either |
関数型コレクションも使うなら vavr 一択 |
| Python | returns (dry-python) |
本番環境向け。型アノテーション充実 |
| Python | result |
軽量。Rust ライクなシンプルな API |
詳細ガイドライン
全言語の実装パターン、エラー型設計の詳細は references/guidelines.md を参照。
関連スキル（併読推奨）
このスキルを使用する際は、以下のスキルも併せて参照すること：
error-classification: エラーの分類（Error, Defect, Fault, Failure）に基づく処理方式の選択domain-building-blocks: ドメイン操作におけるResult/Eitherの適用repository-design: リポジトリのエラー処理パターン（同期・非同期）
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.
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.
- 7d ago First seen · 94 lines · 174 tokens per session scan A 9578dcf9efc5
error-handling is a skill published in the GitHub repository j5ik2o/event-store-adapter-js (24 stars, last pushed yesterday), licensed Apache-2.0. It adds 174 tokens to every session and 1,112 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to error-handling, differing in 0 lines, and is treated as a copy.
Other skills, from other repositories
cratis-lens-browser-extension
Use the Cratis Lens browser extension against a running Cratis Arc application — building and side-loading it, what the Arc app must already serve for Lens to work, switching the active user and tenant, and executing a command or query from the popup. Use when setting Lens up, when Lens does not detect an Arc app, or…
cratis-chronicle-cli-operations
Inspect and operate a running Chronicle server with the cratis CLI - contexts and connection resolution, machine-readable output, failed partitions, observers, event sequences, read models, projections and jobs, and the authorization discipline for replay, retry, quarantine clearing and other mutations. Use when the…
add-traces
Use this skill when asked to add OpenTelemetry tracing to a class in a Cratis Chronicle Kernel project. Produces Traces.cs companion files using the [Span] source-generator pattern from Cratis.Traces, registers IActivitySource as a keyed DI service, and injects it into the target class.
cratis-engineering-chronicle-kernel-tracing
Add OpenTelemetry tracing to a class in the Chronicle repository using the Cratis.Traces [Span] source generator, keyed IActivitySource injection, and the Chronicle tag extensions. Use when instrumenting Chronicle kernel or client internals; this is contributor guidance for the Chronicle repository itself, not for an…
cratis-cli-terminal-workbench
Navigate the cratis CLI's terminal Workbench - the full-screen TUI launched with cratis chronicle workbench. Use when exploring a running Chronicle store interactively rather than answering one question with a single command, when locating an observer, failure, event type, projection or read model by name, or when…
inspect-running-chronicle
Inspect or operate a running Chronicle server with the cratis CLI - list failed partitions, read why an observer is stuck, replay a partition, browse events, event types, read models, projections and jobs. Use when a question is about the state of a live store rather than the source code, when a projection will not…