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cfn-behavior-validator

Creates test stacks, analyzes CloudFormation events, compares actual vs documented update behavior, then confirms whether a resource property change triggers replacement rather than an in-place update. Use when: testing if a CFN property change causes resource replacement; investigating stack update behavior, "Update requires" documentation accuracy; validating whether a workaround (e.g. hash-based logical IDs) is actually necessary; questioning UpdateRequiresReplacement behavior for immutable properties; needing empirical evidence before an architectural decision involving CDK/CloudFormation stack updates.

Quality

89%

Does it follow best practices?

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SecuritybySnyk

Low

Low-risk findings worth noting

SKILL.md
Quality
Evals
Security

Quality

Content

77%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.

The body is an operationally rich, well-sequenced guide with real commands, explicit validation gates, and high-value anti-patterns covering failure modes. Its main defects are a repeated ENI-churn explanation, a stub code example, and a progressive-disclosure failure: it cites a nonexistent EXAMPLES.md and never links the bundled sns-testing-guide.md reference.

Suggestions

Fix the broken reference graph: either add the missing EXAMPLES.md walkthrough or point the sentence at the existing references/sns-testing-guide.md, and add a clearly signaled entry for sns-testing-guide.md (e.g. in a references table alongside the scripts).

Deduplicate the Lambda VPC/ENI-churn explanation — keep it once (in the "No interruption" anti-pattern, where it is load-bearing) and drop the near-verbatim copy from Mindset.

Replace the placeholder TypeScript stack skeleton with a minimal runnable example (a concrete resource and a context-driven property toggle) so the design step is copy-paste executable.

DimensionReasoningScore

Conciseness

The body is dense and nearly every section carries non-obvious operational content (validation gates, rollback recovery, DeletionPolicy timing, jq normalization). The main trim opportunities are the Lambda VPC/ENI-churn passage repeated nearly verbatim in both Mindset and the "No interruption" anti-pattern, and a slightly long Mindset preamble — minor over-explanation, not systemic padding.

4 / 5

Actionability

Mostly executable guidance: real `cdk deploy` and `aws cloudformation describe-stack-events --query` commands, a `continue-update-rollback` recovery command, a jq normalization pipeline, and a findings-report template. The TypeScript stack example is a placeholder skeleton ("Add only the resource under test, driven by this.node.tryGetContext(...)") and commands use `<stack-name>` placeholders, which keeps it just short of copy-paste ready.

4 / 5

Workflow Clarity

The four-step workflow (Research → Design → Execute → Document & Decide) has an explicit "Validation gates" block (stop on failed initial deploy, abort and document on unexpected behavior, repeat on ambiguity) plus a decision framework mandating hypothesis-first testing and repetition before trust. Error-recovery paths are also covered by the UPDATE_ROLLBACK_FAILED anti-pattern with a concrete recovery command — this satisfies the destructive-operation validation requirement fully.

5 / 5

Progressive Disclosure

The scripts table cleanly signals both bundled scripts, but the body points to "EXAMPLES.md in this skill directory" for the full walkthrough and that file does not exist, while the actual bundled reference (references/sns-testing-guide.md) is never linked from SKILL.md. Navigation is therefore broken in both directions — a dead reference and an orphaned file — which is more than a minor organization gap.

3 / 5

Total

16

/

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: concrete third-person actions, an explicit multi-scenario Use-when clause, and good synonym coverage make both capability and triggers unambiguous. The only weakness is mild overlap risk with general CDK/stack-update skills via its broader trigger phrases.

Suggestions

Narrow the broader triggers (e.g. replace "investigating stack update behavior" with "investigating whether a stack update replaces a resource") to reduce overlap with general CDK debugging skills.

Add the plain-English phrasing users often reach for first, such as "will this property change delete and recreate my resource?", to the Use-when list.

DimensionReasoningScore

Specificity

"Creates test stacks, analyzes CloudFormation events, compares actual vs documented update behavior, then confirms whether a resource property change triggers replacement rather than an in-place update" lists four concrete, distinct actions that comprehensively cover the skill's behavior. Third-person voice is used correctly, and nothing is padded or generic.

5 / 5

Completeness

It explicitly answers both questions: a clear "what" (create test stacks, analyze events, compare actual vs documented behavior, confirm replacement vs in-place) and an explicit "Use when:" clause with five concrete trigger scenarios. This matches the anchor-5 example structure exactly.

5 / 5

Trigger Term Quality

The "Use when" list covers natural user phrasings — "testing if a CFN property change causes resource replacement", "investigating stack update behavior", "validating whether a workaround (e.g. hash-based logical IDs) is actually necessary" — with synonym coverage across CFN, CloudFormation, CDK, "Update requires", replacement, and in-place update. Only slightly jargon-y entries like "questioning UpdateRequiresReplacement behavior" keep it from being flawless, but overall coverage is comprehensive.

5 / 5

Distinctiveness Conflict Risk

The core niche — empirically confirming replacement vs in-place update behavior — is distinct with dedicated triggers. However, broader entries like "investigating stack update behavior" and the CDK/CloudFormation references create minor overlap risk with a general aws-cdk or stack-debugging skill (two of which it lists under Related Skills), so it is not fully minimal-conflict.

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

pantheon-org/tekhne

Path

skills/infrastructure/cfn/behavior-validator/SKILL.md

Reviewed

Table of Contents

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