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Agent skill

Swift Error Handling

by HoangNguyen0403 in HoangNguyen0403/agent-skills-standard

Standards for throwing functions, Result type, and Never. An agent skill from HoangNguyen0403/agent-skills-standard.

MITAuto-check passedMobile

Install Swift Error Handling

skills CLI
$ npx skills add HoangNguyen0403/agent-skills-standard --skill swift-error-handling -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install HoangNguyen0403/agent-skills-standard swift-error-handling --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/HoangNguyen0403/agent-skills-standard.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/swift/swift-error-handling .claude/skills/swift-error-handling && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
swift-error-handling
GitHub stars
572
Token cost
~566 tokens
SKILL.md length
235 words
Files
3 (incl. references)
Skills in repo
211
Repo updated
First seen
Licence
MIT

At a glance

Standards for throwing functions, Result type, and Never. An agent skill from HoangNguyen0403/agent-skills-standard.

  • Works in 4 steps: Define custom error enum conforming to… → Mark function throws (or async throws) → Use do-catch at call site with specific… → …
  • Implementing Swift error throwing
  • SKILL.md covers Priority: P0 (CRITICAL), Workflow: Add Error Handling…, Implementation Guidelines and Anti-Patterns, plus 2 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Swift Error Handling is an agent skill from HoangNguyen0403/agent-skills-standard. Standards for throwing functions, Result type, and Never. Use when implementing Swift error throwing, designing error hierarchies, using Result types, or adding do-catch blocks.

Its SKILL.md is about 570 tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including reference files (for example `evals/evals.json` and `references/implementation.md`).

It sits in Mobile, covering iOS development. The repository describes itself as: A collection of Agent Skills Standard and Best Practice for Programming Languages, Frameworks that help our AI Agent follow best practies on frameworks and programming laguages. The licence is MIT.

When your agent uses it

  • Implementing Swift error throwing
  • Designing error hierarchies
  • Using Result types
  • Adding do-catch blocks

Example prompts

  • “Use the swift-error-handling skill to standard for throwing functions, Result type, and Never. An agent skill from…”
  • “/swift-error-handling”

Workflow steps

4 steps, taken from the first numbered list in SKILL.md.

  1. Define custom error enum conforming to Error
  2. Mark function throws (or async throws)
  3. Use do-catch at call site with specific catch clauses
  4. Map domain errors to user-facing messages at presentation layer

What it can do on your machine

Read from SKILL.md and the folder at commit b529c2d. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Swift Error Handling loads about 566 tokens when it runs, and up to ~1.1k if it reads all its reference files. Until then it costs about 50 tokens; SKILL.md has 235 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~50
When it runs · the whole SKILL.md, loaded when a task matches
~566
With references · SKILL.md plus every file in references/, read only if the agent opens them
~1.1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from HoangNguyen0403/agent-skills-standard at commit b529c2d, republished under its MIT licence (© HoangNguyen0403). 235 words, ~566 tokens.

Download SKILL.mdSave it as .claude/skills/swift-error-handling/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.
name
swift-error-handling
description
Standards for throwing functions, Result type, and Never. Use when implementing Swift error throwing, designing error hierarchies, using Result types, or adding do-catch blocks.

Swift Error Handling

Priority: P0 (CRITICAL)

Workflow: Add Error Handling to Swift Function

  1. Define custom error enum conforming to Error
  2. Mark function throws (or async throws)
  3. Use do-catch at call site with specific catch clauses
  4. Map domain errors to user-facing messages at presentation layer

Implementation Guidelines

Throwing Functions
  • Propagate Errors: Use throws for recoverable errors and async throws for modern concurrency.
  • Do-Catch: Handle close to source; specific catch clauses per error type. Catch-all catch: last resort.
  • Error Types: Define custom errors as enums conforming to Error:

See implementation examples for custom error enums, do-catch patterns, and Result type usage.

  • Optional Try: Use try? only for non-critical errors where nil acceptable.
Result Type
  • Async Alternatives: Use throws for synchronous code. Use Result for callbacks and non-async deferred error states.
  • Transformations: Use .map(), .flatMap() for functional composition.
  • Conversion: Use .get() to convert Result to throwing for use in try-catch.
Never Type & Preconditions
  • Fatalisms: Use Never return type only for unrecoverable crash scenarios or to indicate unreachable code. Never for expected errors.
  • Preconditions: Use precondition(), assert(), and fatalError() for programmer errors. Use assertionFailure() for debug-only checks.

Anti-Patterns

  • No try!: Use try? or do-catch.
  • No try? without nil check: Handle or log.
  • No Error(message): Use typed errors.

References

Canonical response anchors

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:

  • Never for expected

© HoangNguyen0403, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files (references) in skills/swift/swift-error-handling of HoangNguyen0403/agent-skills-standard.

  • SKILL.md
  • evals/evals.json
  • references/implementation.md

Open the folder on GitHubat commit b529c2d

Compare with similar skills

Swift Error Handling next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Swift Error Handling compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Swift Error Handling this skillHoangNguyen0403/agent-skills-standard572—~566Automated safety check: PassMIT
Swiftui Protwostraws/SwiftUI-Agent-Skill5.6k2 repos~1.5kAutomated safety check: PassMIT
Swiftui UI PatternsAFK-surf/OpenBridge4304 repos~887Automated safety check: PassMIT
Swiftui Performance Auditharperreed/dotfiles3348 repos~1.4kAutomated safety check: PassNone
Swift Testing ExpertAvdLee/Swift-Testing-Agent-Skill4711 repos~1.2kAutomated safety check: PassMIT
Hig Project Contextraintree-technology/hig-doctor1445 repos~1.2kAutomated safety check: PassMIT

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Categories

Questions about Swift Error Handling

What does Swift Error Handling do?

Standards for throwing functions, Result type, and Never. An agent skill from HoangNguyen0403/agent-skills-standard. Swift Error Handling is an agent skill from HoangNguyen0403/agent-skills-standard. Standards for throwing functions, Result type, and Never.

When should I use Swift Error Handling?

Swift Error Handling fits situations like: implementing Swift error throwing; designing error hierarchies; using Result types; adding do-catch blocks.

How do I install Swift Error Handling in Claude Code?

Run `npx skills add HoangNguyen0403/agent-skills-standard --skill swift-error-handling -a claude-code`. Or copy the skill folder (skills/swift/swift-error-handling in HoangNguyen0403/agent-skills-standard) into .claude/skills/swift-error-handling in your project. Claude Code loads it when a task matches its description.

How do I install Swift Error Handling in Codex?

Run `npx skills add HoangNguyen0403/agent-skills-standard --skill swift-error-handling -a codex`. Or copy the skill folder (skills/swift/swift-error-handling in HoangNguyen0403/agent-skills-standard) into .agents/skills/swift-error-handling in your project. Codex loads it when a task matches its description.

Can I use Swift Error Handling in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add HoangNguyen0403/agent-skills-standard --skill swift-error-handling -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/swift-error-handling, .gemini/skills/swift-error-handling, .github/skills/swift-error-handling and .opencode/skills/swift-error-handling in your project.

What does Swift Error Handling need to run?

SKILL.md names no scripts, command-line tools or credentials: Swift Error Handling is instructions for the agent only.

Does Swift Error Handling access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Swift Error Handling safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Swift Error Handling use?

Swift Error Handling is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Swift Error Handling use?

About 566 tokens (SKILL.md is roughly 2.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 580 tokens, read only when the agent opens those files.

What are the alternatives to Swift Error Handling?

Skills that share tags, products or a category with Swift Error Handling: Swiftui Pro (twostraws/SwiftUI-Agent-Skill, 5.6k stars), Swiftui UI Patterns (AFK-surf/OpenBridge, 430 stars), Swiftui Performance Audit (harperreed/dotfiles, 334 stars) and Swift Testing Expert (AvdLee/Swift-Testing-Agent-Skill, 471 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Swift Error Handling?

HoangNguyen0403 (a GitHub user) maintains it in HoangNguyen0403/agent-skills-standard, which has 572 GitHub stars. The repository holds 211 skills in this directory. The repository was last updated on October 9, 2026.

Source: HoangNguyen0403/agent-skills-standard on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.