type-level-error-messages

Make compile-time errors readable by branding constraint-violation types as template literal messages with a U+200B zero-width-space suffix. Use when writing helper functions that constrain object keys, string shapes, or other literal-type inputs and you want the TypeScript error tooltip to read as an English sentence pointing at the offending value.

Quality

96%

Does it follow best practices?

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Securityby

Passed

No findings from the security scan

Quality

Content

92%

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

An excellent, actionable, concise code skill with executable examples and a real validation feedback loop. The main gap is progressive disclosure: substantial reference-grade material (full predicate anatomy, extended pitfalls) lives inline rather than in well-signaled separate files.

Suggestions

Move the full recursive predicate anatomy and the extended pitfalls/alternatives sections into a single references file (e.g. references/predicates-and-pitfalls.md) and link to it from a concise SKILL.md overview, keeping only the headline example inline.

Verify that the file paths in the Reference section (node_modules/@ark/util/out/errors.d.ts:25, packages/workspace/src/shared/actions.ts) resolve to real files, or mark them as illustrative so progressive_disclosure can be scored against actual bundle structure.

Consider promoting the 'Why not arkregex / never / unique symbol' comparison table into its own reference doc so SKILL.md stays a focused quick-start overview.

Dimension	Reasoning	Score
Conciseness	Lean and dense: every section earns its place (the pattern, the U+200B rationale, predicate anatomy, alternatives, pitfalls) without explaining basic TS concepts Claude already knows.	3 / 3
Actionability	Provides fully executable, copy-paste-ready code — the InvalidKey branded type, the recursive IsSnakeCase predicate, the runtime-checked defineActions helper — with concrete examples and exact regexes.	3 / 3
Workflow Clarity	The runtime-check section pairs the type-level check with a validating runtime guard and a test that exercises the bypass branch (expect().toThrow), giving an explicit validate→fix feedback loop for the destructive bypass cases it enumerates.	3 / 3
Progressive Disclosure	Content is well-organized into clear sections, but the recursive predicate anatomy, alternatives, and pitfalls are all inline in SKILL.md rather than split into one-level-deep reference files; no bundle files exist to offload the deeper material.	2 / 3
	Total	11 / 12 Passed

Description

100%

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

A highly specific, third-person description that cleanly states both what it does and when to use it, with low conflict risk against general TypeScript skills. Slightly jargon-dense but the trigger terms map naturally to real requests.

Dimension	Reasoning	Score
Specificity	Lists multiple concrete actions — branding 'constraint-violation types as template literal messages' and appending 'a U+200B zero-width-space suffix' — rather than vague domain language.	3 / 3
Completeness	Explicitly answers what (make compile-time errors readable via branded template literals) and when ('Use when writing helper functions that constrain object keys, string shapes, or other literal-type inputs').	3 / 3
Trigger Term Quality	Includes natural terms a user would say — 'helper functions', 'constrain object keys', 'string shapes', 'TypeScript error tooltip' — covering the main ways this need surfaces.	3 / 3
Distinctiveness Conflict Risk	The niche is precise — branded type-level error messages for constrained literal inputs — and unlikely to trigger for general TypeScript skills; triggers are tightly scoped.	3 / 3
	Total	12 / 12 Passed

Validation

100%

Warnings & errors only

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 16 / 16 Passed

Validation for skill structure

No warnings or errors.

Repository: EpicenterHQ/epicenter
Path: .agents/skills/type-level-error-messages/SKILL.md
Commit: cb12bcc

Reviewed: 3 days ago

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