The body is lean (under ~50 lines), assumes Claude's competence, and adds no tutorial filler explaining what Spring Security or CSRF is — every section earns its place. Matches the score-3 anchor of lean, efficient content. Not score 2 because there is no unnecessary explanation or padding to tighten.

Concrete, executable commands are present ("Run `./mvnw compile`", "Run `./mvnw clean verify`") and a specific reference path is named, but the core security guidance is delegated entirely to the external reference with no inline examples of SecurityFilterChain/@PreAuthorize patterns to act on. Matches the score-2 anchor of some concrete guidance but incomplete; not score 3 because key implementation details are not executable in-place, and not score 1 because real commands and a concrete reference path are given.

A clear 4-step sequence is given (read reference → gather scope → apply changes → verify) with explicit validation checkpoints: "MANDATORY: Run `./mvnw compile`... before applying any change", "SAFETY: If compilation fails, stop immediately", and "VERIFY: Run `./mvnw clean verify`... after applying improvements". This matches the score-3 anchor of a clear sequence with explicit validation and a safety feedback loop. Not score 2 because validation checkpoints and the stop-on-failure loop are explicit.

SKILL.md is a concise overview that signals a single one-level-deep reference ([references/304-frameworks-spring-boot-security.md](references/304-frameworks-spring-boot-security.md)), and that file exists in the bundle, with the reference named consistently in the Workflow and Reference sections. Matches the score-3 anchor of a clear overview with well-signaled one-level-deep references. Not score 2 because navigation is clear and the reference is real and not deeply nested.

Lists many concrete actions and objects — "design, review, or improve security", "SecurityFilterChain, OAuth2/JWT resource server patterns, form login basics, method security (@PreAuthorize), CSRF and CORS for APIs, session fixation, security headers, exception handling, password encoding, and sensitive-data-safe logging" — matching the score-3 anchor of multiple specific concrete actions. Not score 2 because the enumeration is comprehensive rather than a partial domain mention.

It answers both what ("design, review, or improve security in Spring Boot applications — including SecurityFilterChain, OAuth2/JWT...") and when ("Use when you need to..." plus "This should trigger for requests such as...") with explicit triggers, matching the score-3 anchor. Not score 2 because an explicit 'when' clause is present rather than merely implied.

Explicit natural trigger phrases users would say are given verbatim: "Add Spring Boot security support; Review Spring Boot security configuration; Improve API authorization in Spring Boot; Add JWT resource server security in Spring Boot; Harden Spring Boot security headers and CSRF settings". This matches the score-3 anchor of good coverage of natural terms. Not score 2 because the triggers are varied, natural request sentences rather than sparse keyword coverage.

Scoped tightly to Spring Boot security with distinctive terms (SecurityFilterChain, @PreAuthorize, JWT resource server) that are unlikely to fire for non-Spring or non-security skills, matching the score-3 clear-niche anchor. The "Part of Plinth Toolkit" suffix is harmless provenance. Not score 2 because the niche is concrete and the triggers are domain-specific rather than overlapping with generic skills.