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fastly

Configures, manages, and debugs the Fastly CDN platform — covering service and backend setup, caching and VCL, security features like DDoS/WAF/NGWAF/rate limiting/bot management, TLS certificates and cache purging, the Compute platform, and the REST API. Use when working with Fastly services or domains, setting up edge caching or origin shielding, configuring security features, making Fastly API calls, enabling products, or looking up Fastly documentation. Also applies when troubleshooting 503 errors or SSL/TLS certificate mismatches on Fastly, and for configuring logging endpoints, load balancing, ACLs, or edge dictionaries. Read the relevant reference file before writing any Fastly API call or curl command — request field names (e.g. the backend fields override_host, ssl_cert_hostname, ssl_sni_hostname, use_ssl) are easy to misremember, and a wrong name causes a silent 503 instead of an error, so do not rely on training-knowledge field names.

80

Quality

100%

Does it follow best practices?

Impact

No eval scenarios have been run

SecuritybySnyk

Advisory

Suggest reviewing before use

SKILL.md
Quality
Evals
Security

Quality

Content

100%

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

This is an exceptionally well-crafted skill that demonstrates mastery of the format. It provides high-value, actionable VCL recipes targeting genuinely error-prone patterns (Vary header append, cookie parsing, grace detection), includes critical safety guidance (token handling, pre-flight checks), and organizes 20+ topic areas into a clean progressive disclosure table. The common mistakes section alone would prevent numerous silent 503 errors and debugging sessions.

DimensionReasoningScore

Conciseness

The content is lean and efficient throughout. It assumes Claude's competence with VCL, CDN concepts, and API usage. Every section earns its place — the VCL recipes address genuinely tricky gotchas (grace detection, Vary append, cookie parsing) rather than explaining basic concepts. The 'Common Mistakes' section is a high-value, compact list of non-obvious pitfalls.

3 / 3

Actionability

All VCL recipes are fully executable, copy-paste ready code with correct syntax. The pre-flight checks provide specific curl and openssl commands. Each recipe includes not just the code but the critical context about where it must be placed (e.g., vcl_fetch vs vcl_deliver) and why alternatives fail. The common mistakes section provides concrete corrections.

3 / 3

Workflow Clarity

The Quick Start section provides a clear sequenced workflow with explicit pre-flight validation checks (verify origin responds, check TLS SANs) before any configuration. The VCL recipes each include clear placement guidance and warnings about incorrect approaches. The skill appropriately delegates the full step-by-step workflow to the CLI skill's reference, keeping this skill focused.

3 / 3

Progressive Disclosure

Excellent progressive disclosure with a well-organized topic table providing 20+ one-level-deep references with clear 'Use when...' descriptions. The main SKILL.md contains a concise overview, common recipes, and quick start, while detailed topics are cleanly separated into reference files. Navigation is intuitive with the table format.

3 / 3

Total

12

/

12

Passed

Description

100%

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

This is an excellent skill description that thoroughly covers the Fastly CDN domain with specific actions, comprehensive trigger terms, and clear guidance on when to use it. It goes beyond the basics by including operational wisdom about field name pitfalls and the instruction to consult reference files before making API calls. The description is well-structured, uses third person voice correctly, and would be highly distinguishable from other skills in a large skill library.

DimensionReasoningScore

Specificity

Lists multiple specific concrete actions: configures/manages/debugs Fastly CDN, covering service/backend setup, caching and VCL, security features (DDoS/WAF/NGWAF/rate limiting/bot management), TLS certificates, cache purging, Compute platform, REST API, logging endpoints, load balancing, ACLs, edge dictionaries.

3 / 3

Completeness

Clearly answers both 'what' (configures, manages, debugs Fastly CDN with detailed feature list) and 'when' with explicit 'Use when...' clause covering multiple trigger scenarios including troubleshooting 503 errors, SSL/TLS issues, API calls, and configuring various Fastly features.

3 / 3

Trigger Term Quality

Excellent coverage of natural terms users would say: Fastly, CDN, VCL, DDoS, WAF, NGWAF, rate limiting, bot management, TLS, SSL, cache purging, 503 errors, edge caching, origin shielding, Fastly API, curl, ACLs, edge dictionaries, logging endpoints, load balancing, certificate mismatches.

3 / 3

Distinctiveness Conflict Risk

Highly distinctive — clearly scoped to the Fastly CDN platform specifically, with Fastly-specific terminology (VCL, NGWAF, origin shielding, edge dictionaries, Compute platform) that would not conflict with generic CDN or web server skills.

3 / 3

Total

12

/

12

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.

Validation11 / 11 Passed

Validation for skill structure

No warnings or errors.

Repository
fastly/fastly-agent-toolkit
Reviewed

Table of Contents

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