Conciseness

The body is lean — tables, code skeletons, and terse rules with zero explanation of concepts Claude already knows — but there are minor instances that could be trimmed: the Anti-patterns section restates ~5 rules already given in Step 2 ("Endpoint sin response_model=", "Repo sin tenant_id param", "Migration no idempotente", "sa.Enum(create_type=True)"), and the version-pinned "broken SA 2.0.27" is time-sensitive info not placed in an old-patterns/deprecated section. This fits anchor 4 (efficient with minor trimmable instances) better than anchor 5, where every token would earn its place.

Actionability

Guidance is fully concrete: an executable grep/find block with real paths ("grep -rn \"<kw>\" backend/src/core/"), exact decision thresholds ("Match en shared 80%+ overlap → EXTEND"), copy-shaped code skeletons for DTOs/domain/SQLA/migrations ("op.execute(\"CREATE TABLE IF NOT EXISTS ...\")"), exact test file paths ("tests/modules/{m}/test_{name}_endpoint.py"), and an explicit handoff path. Per the code-vs-instruction note, this instruction skill's guidance is specific and executable with specific examples covering the common cases — matching anchor 5; the placeholders ({module}, <kw>) are the skill's intended template variables, not pseudocode.

Workflow Clarity

Steps 1–4 are clearly sequenced with real checkpoints: the audit decision framework in Step 1 (EXTEND/EXTEND con caveat/NEW with a required justification section) and the Step 3 hard gate ("Sin esto + flip → builder REVIEW FAIL automático"), plus the Anti-patterns checklist. This exceeds anchor 4's 'most checkpoints present' but falls short of anchor 5, which requires feedback loops for error recovery — there is no guidance for what to do when a checkpoint fails (e.g., audit finds a partial match mid-design, or the template file is missing).

Progressive Disclosure

The skill is a single well-sectioned file (Workflow steps, Anti-patterns, Output format) with no nested references and easy navigation, and no bundle files exist to organize — but the core instructions depend on an external template ("Seguir template docs/specs/templates/03-arch-template.md") that is not bundled or clearly located, and at ~150 lines the code skeletons could arguably live in a reference file. This fits anchor 4 (good structure, minor organization gaps) rather than anchor 5 (content appropriately split with well-signaled references).

Specificity

"Produce 03-arch-be.md con: endpoints, DTOs Pydantic, SQLA models, migrations idempotent, services, repositories, tests requeridos, cross-cutting (tenant isolation, currency, master-data, PII)" lists multiple specific concrete actions with comprehensive coverage, and inputs are named too ("Lee 01-spec.md + (02-design-ui.md si mixed) + story YAML"). This matches the anchor 5 example (multiple specific actions, comprehensive) rather than anchor 4, which allows minor coverage gaps — no meaningful capability is left unnamed.

Completeness

What is explicit ("Produce 03-arch-be.md con: endpoints, DTOs Pydantic, ...") and when is explicit with concrete trigger phrases ("Activa cuando /architect spawna o user dice: '/architect-be', 'arq backend', 'diseña BE'"), matching anchor 5 exactly. The 'Use when' equivalent clause is present, so the completeness cap of 3 does not apply.

Trigger Term Quality

"Activa cuando /architect spawna o user dice: '/architect-be', 'arq backend', 'diseña BE'" gives three explicit, natural trigger phrases a user would actually say, matching anchor 4's good keyword coverage. Not 5 because it lacks synonym/variation coverage (e.g. 'diseño backend', 'backend architecture', or English equivalents); not 3 because the triggers are explicit and quoted rather than merely 'some relevant keywords'.

Distinctiveness Conflict Risk

"Sub-architect Backend" plus backend-specific triggers ('arq backend', 'diseña BE') carve a clear niche, mostly matching anchor 4. Not 5 because the description does not disambiguate against the sibling sub-architects (/architect-fe, /architect-agentic) or the parent /architect orchestrator, leaving minor overlap risk; not 3 because the triggers are distinct enough that wrong-skill activation is unlikely.