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legacy-modernizer

Designs incremental migration strategies, identifies service boundaries, produces dependency maps and migration roadmaps, and generates API facade designs for aging codebases. Use when modernizing legacy systems, implementing strangler fig pattern or branch by abstraction, decomposing monoliths, upgrading frameworks or languages, or reducing technical debt without disrupting business operations.

73

Quality

92%

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SKILL.md
Quality
Evals
Security

Quality

Content

85%Weight 40%Scale 1-5

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

A well-structured body: a five-phase workflow with validation checkpoints on every step, correctly-scoped code examples, a hard constraints section, and clean progressive disclosure into five real reference files. The remaining gains are trimming concept-list padding and de-duplicating the feature-flag example, plus making the early workflow steps as concrete as the later ones.

Suggestions

Remove the 'Knowledge Reference' buzzword list (strangler fig pattern, feature flags, canary deployments, etc.) — Claude already knows these concepts and the list adds no actionable guidance; the lowest-hanging conciseness fix.

Drop or merge the 'Feature Flag Wrapper' example: it duplicates the env-var check already demonstrated inside the facade example; referencing a shared flag_enabled helper from the facade would halve that code while keeping coverage.

Tighten actionability of the early workflow steps by naming the concrete artifacts to use, e.g. pointing step 1's dependency map and step 2's roadmap directly at the LegacyCodeAnalyzer checklist and templates in references/system-assessment.md.

DimensionReasoningScore

Conciseness

The workflow, constraints, and output templates are tight, but there are trimmable pieces: the "Knowledge Reference" section is a list of concepts Claude already knows ("Strangler fig pattern, branch by abstraction, characterization testing, ... zero-downtime deployment"), and the Feature Flag Wrapper example repeats the env-var flag logic already shown in the facade example. This fits anchor 4 ("Efficient; minor instances of over-explanation that could be trimmed") — not score 5, where every token would earn its place, and not score 3, since the padding is peripheral rather than woven through the guidance.

4 / 5

Actionability

The code examples (facade, feature flag, characterization test) are complete, executable Python with concrete thresholds ("Target 80%+ coverage", "5% → 25% → 50% → 100%"), but they reference hypothetical services (legacy_service/new_service) and workflow steps like "Produce a dependency map and risk register" stay directional, deferring specifics to reference files. Anchor 4 ("Mostly executable guidance; concrete code or commands with minor gaps") is the best fit; score 5 would require the examples to stand alone covering the common cases without deferring key detail.

4 / 5

Workflow Clarity

The five-step Core Workflow is clearly sequenced and every step carries an explicit validation checkpoint ("Confirm all external integrations and data contracts are documented", "Run the characterization test suite and confirm it passes green on the unmodified legacy system", "Verify error rates and latency metrics remain within baseline thresholds after each traffic increment"), with rollback triggers defined per phase. This matches anchor 5 ("Clear sequence with explicit validation steps; feedback loops for error recovery"); score 4 would leave some checkpoints implicit, which is not the case here.

5 / 5

Progressive Disclosure

The Reference Guide table signals each of the five one-level-deep reference files (all verified to exist and be substantive) with a "Load When" condition — e.g. "`references/strangler-fig-pattern.md` | Incremental replacement, facade layer, routing" — and the detailed guidance is appropriately split out of the overview. This is a direct match for anchor 5 ("Clear overview with well-signaled one-level-deep references; content appropriately split; easy navigation"); score 4 would have less clearly signaled or less cleanly split references.

5 / 5

Total

18

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20

Passed

Description

96%Weight 40%Scale 1-5

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 strong description in third-person voice that pairs a concrete capability list with an explicit, pattern-aware "Use when" trigger clause. Its only weakness is a couple of broad trigger terms (technical debt, framework upgrades) that create minor overlap risk with general refactoring skills.

DimensionReasoningScore

Specificity

The description lists multiple concrete actions — "Designs incremental migration strategies, identifies service boundaries, produces dependency maps and migration roadmaps, and generates API facade designs" — giving comprehensive coverage of the skill's capabilities. This matches the anchor "Lists multiple specific concrete actions; comprehensive coverage"; it is not score 4, which requires minor gaps in coverage.

5 / 5

Completeness

Both questions are answered explicitly: the "what" is the opening capability list, and the "when" is the concrete trigger clause "Use when modernizing legacy systems, implementing strangler fig pattern..., decomposing monoliths, upgrading frameworks or languages, or reducing technical debt". This is a direct match for the anchor-5 example structure and clearly above score 4, where the "when" would be less specific.

5 / 5

Trigger Term Quality

The "Use when" clause covers the natural phrases a user would say: "modernizing legacy systems", "implementing strangler fig pattern or branch by abstraction", "decomposing monoliths", "upgrading frameworks or languages", "reducing technical debt" — including synonyms and pattern-level variations. No common domain phrasing is missing, so it fits the comprehensive anchor rather than score 4 ("a few natural terms missing").

5 / 5

Distinctiveness Conflict Risk

The niche is clear (legacy/aging-codebase modernization with distinct pattern triggers like "strangler fig" and "decomposing monoliths"), but "reducing technical debt" and "upgrading frameworks or languages" are broad triggers that overlap with general refactoring and devops skills. This fits anchor 4 ("Mostly distinct; minor overlap risk with closely related skills") better than 5 ("minimal conflict risk"), since a general tech-debt request would plausibly fire this skill.

4 / 5

Total

19

/

20

Passed

Validation

100%

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

Jeffallan/claude-skills

Path

skills/legacy-modernizer/SKILL.md

Reviewed

Table of Contents

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