New: 98,000+ skills indexed from GitHub repos with 100+ stars · every skill safety-checkedBrowse top skillsTop skills
Esc to closeBrowse all skills
Submit a skillBrowse skills
Submit a skillBrowse skills

Agent skill

Type Level Error Messages

by EpicenterHQ in EpicenterHQ/epicenter

Make TypeScript errors readable with template-literal constraint messages.

Custom licenceAuto-check: warnings

Install Type Level Error Messages

The automated check flagged lines worth reading first. See the safety section below.

skills CLI
$ npx skills add EpicenterHQ/epicenter --skill type-level-error-messages -a claude-code

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

GitHub CLI
$ gh skill install EpicenterHQ/epicenter type-level-error-messages --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/EpicenterHQ/epicenter.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/type-level-error-messages .claude/skills/type-level-error-messages && 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
type-level-error-messages
GitHub stars
4.8k
Token cost
~2k tokens
SKILL.md length
710 words
Files
1
Skills in repo
65
Repo updated
First seen
Licence
Custom licence

At a glance

Make TypeScript errors readable with template-literal constraint messages.

  • Works in 2 steps: Autocomplete hygiene. Without the brand,… → Distinct from S extends string. Other…
  • Constraining literal object keys
  • SKILL.md covers The pattern in one example, Why the U+200B suffix, Anatomy of a constraint… and Why not arkregex, plus 5 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Type Level Error Messages is an agent skill from EpicenterHQ/epicenter. Make TypeScript errors readable with template-literal constraint messages. Use when constraining literal object keys or string shapes and the error should point to the offending value.

Its SKILL.md is about 2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It works with TypeScript. The repository describes itself as: Open-source, local-first apps.

When your agent uses it

  • Constraining literal object keys
  • String shapes and the error should point to the offending value

Example prompts

  • “/type-level-error-messages”

Workflow steps

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

  1. Autocomplete hygiene. Without the brand, if anywhere in the codebase the inferred type happens to be Invalid action key "..."…
  2. Distinct from S extends string. Other type machinery that narrows against arbitrary string subtypes can otherwise accidentally accept the…

What it can do on your machine

Read from SKILL.md and the folder at commit 9cc65c3. 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 (its code samples are typescript).

    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

Type Level Error Messages loads about 2k tokens when it runs. Until then it costs about 53 tokens; SKILL.md has 710 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~53
When it runs · the whole SKILL.md, loaded when a task matches
~2k

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: warnings

The automated check found patterns that need a careful read before installing.

  • WarningContains zero-width charactersSKILL.md:19
    // 2. Branded error type. The trailing ⟨U+200B⟩ is a zero-width space.
  • WarningContains zero-width charactersSKILL.md:21
    _case ASCII matching /^[a-z][a-z0-9_]*$/⟨U+200B⟩`;
  • WarningContains zero-width charactersSKILL.md:48
    Append `⟨U+200B⟩` (Unicode zero-width space, U+200B) to the error message string. Invisible in IDE tooltips, but it brands the

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

Its licence (Custom licence) doesn't allow us to republish the file, so here is its outline and opening line. It has 710 words (~2,024 tokens).

“A consumer writing a bad key sees:”

— opening of SKILL.md by EpicenterHQ, Custom licence
name
type-level-error-messages
metadata.author
epicenter
metadata.version
1.0

Read the full SKILL.md on GitHub

Files

Just SKILL.md in .agents/skills/type-level-error-messages of EpicenterHQ/epicenter.

Open the folder on GitHubat commit 9cc65c3

Compare with similar skills

Type Level Error Messages 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.

Type Level Error Messages compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Type Level Error Messages this skillEpicenterHQ/epicenter4.8k—~2kAutomated safety check: WarnCustom licence
MCP Server Builderanthropics/skills180k64 repos~2.3kAutomated safety check: PassApache-2.0
Web Artifacts Builderanthropics/skills180k41 repos~769Automated safety check: PassApache-2.0
Typescript Advanced Typesrolling-scopes/rsschool-app10k25 repos~4.2kAutomated safety check: PassMPL-2.0
Code Review ChecklistshareAI-lab/learn-claude-code78k5 repos~1.1kAutomated safety check: PassMIT
MCP Server BuildershareAI-lab/learn-claude-code78k5 repos~1.2kAutomated safety check: PassMIT

Similar skills

  • MCP Server Builder

    anthropics/skills

    Official

    Guides the design and implementation of Model Context Protocol servers in TypeScript or Python, from tool naming and error messages to evaluation.

    180k GitHub starsUsed in 64 repos~2.3k tokens
    Agent WorkflowsAuto-check passed

  • Web Artifacts Builder

    anthropics/skills

    Official

    Builds multi-component claude.ai HTML artifacts as a small React, TypeScript and Tailwind project, then bundles it into one shareable HTML file.

    180k GitHub starsUsed in 41 repos~769 tokens
    Frontend & DesignAuto-check passed

  • Typescript Advanced Types

    rolling-scopes/rsschool-app

    Master TypeScript's advanced type system including generics, conditional types, mapped types, template literals, and utility types for building type-safe applications.

    10k GitHub starsUsed in 25 repos~4.2k tokens
    DevelopmentAuto-check passed

  • Code Review Checklist

    shareAI-lab/learn-claude-code

    Reviews code against a five-part checklist covering security, correctness, performance, maintainability and testing, and reports findings in a fixed format.

    78k GitHub starsUsed in 5 repos~1.1k tokens
    DevelopmentAuto-check passed

  • MCP Server Builder

    shareAI-lab/learn-claude-code

    Walks through building MCP servers in Python or TypeScript that expose tools, resources and prompts to Claude, with templates, registration and testing.

    78k GitHub starsUsed in 5 repos~1.2k tokens
    Agent WorkflowsAuto-check passed

  • Nx Import

    nrwl/nx

    Import, merge, or combine repositories into an Nx workspace using nx import.

    29k GitHub starsUsed in 6 repos~3.5k tokens
    DevelopmentAuto-check passed

More from EpicenterHQ/epicenter

All 65 skills in this repo

  • Agent Instructions

    EpicenterHQ/epicenter

    Write and maintain repository guidance across AGENTS.md, CLAUDE.md, and .agents/skills.

    4.8k GitHub stars~1.2k tokensUpdated yesterday
    Auto-check passed

  • Consult Claude

    EpicenterHQ/epicenter

    Assign Claude Code a read-only investigation, recommendation, or finished text draft.

    4.8k GitHub stars~2k tokensUpdated yesterday
    Auto-check passed

  • Better Auth Security Best Practices

    EpicenterHQ/epicenter

    Better Auth security hardening: rate limits, secrets, CSRF, trusted origins, cookies, sessions, OAuth tokens, and audit logging.

    4.8k GitHub stars~896 tokensUpdated yesterday
    Auto-check passed

  • Cohesion Over Testability

    EpicenterHQ/epicenter

    Collapse test-shaped production boundaries while preserving behavior and coverage.

    4.8k GitHub stars~2k tokensUpdated yesterday
    Auto-check passed

  • Collapse Pass

    EpicenterHQ/epicenter

    Remove indirection that does not earn its boundary across a diff or package.

    4.8k GitHub stars~2k tokensUpdated yesterday
    Auto-check passed

  • Error Handling

    EpicenterHQ/epicenter

    Apply Wellcrafted Result patterns to fallible operations and preserve failures at boundaries.

    4.8k GitHub stars~1.4k tokensUpdated yesterday
    Auto-check passed

Works with

Questions about Type Level Error Messages

What does Type Level Error Messages do?

Make TypeScript errors readable with template-literal constraint messages. Type Level Error Messages is an agent skill from EpicenterHQ/epicenter. Make TypeScript errors readable with template-literal constraint messages.

When should I use Type Level Error Messages?

Type Level Error Messages fits situations like: constraining literal object keys; string shapes and the error should point to the offending value.

How do I install Type Level Error Messages in Claude Code?

Run `npx skills add EpicenterHQ/epicenter --skill type-level-error-messages -a claude-code`. Or copy the skill folder (.agents/skills/type-level-error-messages in EpicenterHQ/epicenter) into .claude/skills/type-level-error-messages in your project. Claude Code loads it when a task matches its description.

How do I install Type Level Error Messages in Codex?

Run `npx skills add EpicenterHQ/epicenter --skill type-level-error-messages -a codex`. Or copy the skill folder (.agents/skills/type-level-error-messages in EpicenterHQ/epicenter) into .agents/skills/type-level-error-messages in your project. Codex loads it when a task matches its description.

Can I use Type Level Error Messages 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 EpicenterHQ/epicenter --skill type-level-error-messages -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/type-level-error-messages, .gemini/skills/type-level-error-messages, .github/skills/type-level-error-messages and .opencode/skills/type-level-error-messages in your project.

What does Type Level Error Messages need to run?

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

Does Type Level Error Messages 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 Type Level Error Messages safe to install?

Our automated static check of SKILL.md flagged 3 warning(s): contains zero-width characters. Read the flagged lines before installing; the check is not a guarantee either way.

What licence does Type Level Error Messages use?

Type Level Error Messages has a licence file (the repository's licence) that doesn't match a standard licence. Read it on GitHub before reusing the skill.

How many tokens does Type Level Error Messages use?

About 2k tokens (SKILL.md is roughly 8.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Type Level Error Messages?

Skills that share tags, products or a category with Type Level Error Messages: MCP Server Builder (anthropics/skills, 180k stars), Web Artifacts Builder (anthropics/skills, 180k stars), Typescript Advanced Types (rolling-scopes/rsschool-app, 10k stars) and Code Review Checklist (shareAI-lab/learn-claude-code, 78k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Type Level Error Messages?

EpicenterHQ (a GitHub organization) maintains it in EpicenterHQ/epicenter, which has 4,819 GitHub stars. The repository holds 65 skills in this directory. The repository was last updated on October 8, 2026.

Source: EpicenterHQ/epicenter on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.