Conciseness

The body is dense and opinionated with no padding of concepts Claude already knows, opening with a pointed stat ('301 distinct environment variables') and assuming domain fluency. A few narrative asides ('This skill exists so the next value does not do the same thing') could be trimmed, keeping it just below the leanest 5.

Actionability

It gives concrete, near-executable guidance: real file paths ('packages/core/src/app-config/'), a complete z.object example with .meta({ env }), and a defineAppConfig plugin example. The examples are mostly copy-paste ready but are illustrative fragments rather than covering every common case, so it sits at 4.

Workflow Clarity

The 'Adding a field' section lays out a clear sequence (domain file -> schema.ts line -> read via getAppConfig -> set from server/plugins/config.ts -> add descriptor + parser coverage), and resolution order is explicit. Checkpoints are implicit rather than bolded validate-then-proceed steps, so it does not reach the explicit-validation 5.

Progressive Disclosure

Content is well organized into clear sections (The rule, Where a value goes, Adding a field, Resolution order, Config or registry?, Antipatterns, Deprecated paths) with one-level references ('see the secrets skill', a plan file). No bundle files exist and nothing clearly belongs in a separate file, but at 165 lines it exceeds the simple-skill 50-line exception that would allow a 5.

Specificity

Names concrete placement surfaces ('app config schema, agent-native.config.ts, or an environment variable') and several concrete trigger actions ('adding an env var, a configure*/set* function, a plugin option, or a register* function'). It lists several specific actions, but the framing is about where a value belongs rather than an exhaustive enumerated verb set, so it stops short of the fully comprehensive 5.

Completeness

It explicitly answers both what ('Where a configuration value belongs ... and how the layers resolve') and when ('Use before adding an env var ... and when deciding whether something is config or a registry') with concrete trigger phrases, matching the top anchor.

Trigger Term Quality

Trigger terms like 'env var', 'configure*/set* function', 'plugin option', and 'register* function' are phrases a developer on this codebase would naturally say. Coverage is good and domain-appropriate, though it leans on internal jargon and omits a few common synonyms, keeping it just below the comprehensive 5.

Distinctiveness Conflict Risk

It carves a clear niche — config-value placement across named internal surfaces — with distinct triggers ('config or a registry', 'register* function') that are unlikely to fire for unrelated skills, giving minimal conflict risk.