The body is lean and avoids re-explaining concepts Claude already knows, but the "What is covered in this Skill?" bullet list and the "When to use this skill" list largely duplicate content already in the description, so not every token earns its place. It is mostly efficient but could be tightened, matching the level-2 anchor and falling below level 3.

Concrete commands appear ("./mvnw compile", "./mvnw clean verify", "ApplicationModules.verify()", "@ApplicationModuleTest"), but the core application guidance in step 3 is abstract ("Add or refine Spring Modulith dependencies, package annotations, architecture verification tests, domain events") with no executable code or annotation examples in the body — key details are deferred to the reference. This matches some-concrete-but-incomplete and is not level 3 (no copy-paste-ready examples).

The four-step Workflow is clearly sequenced and paired with explicit validation checkpoints in Constraints: MANDATORY compile before changes, SAFETY "If compilation fails, stop immediately", and VERIFY via "./mvnw clean verify" after improvements — a clear feedback loop for risky build/architecture changes, matching the level-3 anchor.

The body is an overview that points to a single one-level-deep reference, references/305-frameworks-spring-boot-modulith.md, clearly signaled in both Workflow step 1 and the Reference section; the reference file exists and content is appropriately split, matching the clear-overview-with-well-signaled-references anchor.

Lists many concrete capabilities spanning the Spring Modulith surface area: "application module package structure, ApplicationModules verification, named interfaces, allowed dependencies, domain events, @ApplicationModuleTest, Scenario-based module tests, generated documentation, actuator exposure, observability, and event publication registry choices" — matching the multiple-specific-actions anchor.

Both what and when are explicit: the opening "Use when you need to design, review, or improve modular monoliths with Spring Modulith..." states the capability, and "This should trigger for requests such as..." provides explicit when-triggers, satisfying the both-what-and-when anchor.

Explicit trigger phrases match what a user would naturally say: "Add Spring Modulith to a Spring Boot application", "Review Spring Modulith module boundaries", "Improve modular monolith architecture in Spring Boot", "Add @ApplicationModuleTest tests", "Generate Spring Modulith documentation", giving good natural-term coverage.

The niche is narrow and specific (Spring Modulith within Spring Boot) with distinct triggers, making it unlikely to fire for unrelated skills; the third-person voice is maintained with no first/second-person phrasing.