email-gateway
Multi-provider email sending for Cloudflare Workers and Node.js applications. Build transactional email systems with Resend (React Email support), SendGrid (enterprise scale), Mailgun (developer webhooks), or SMTP2Go (reliable relay). Includes template patterns, webhook verification, attachment handling, and error recovery. Use when sending emails via API, handling bounces/complaints, or migrating between providers.
Overall
score
80%
Does it follow best practices?
If you maintain this skill, you can automatically optimize it using the tessl CLI to improve its score:
npx tessl skill review --optimize ./path/to/skillValidation for skill structure
Discovery
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 hits all the marks. It provides specific capabilities with named providers and their strengths, uses natural trigger terms users would actually search for, includes an explicit 'Use when' clause with clear triggers, and carves out a distinctive niche in the email-sending space for specific runtime environments.
| Dimension | Reasoning | Score |
|---|---|---|
Specificity | Lists multiple concrete actions: 'Build transactional email systems', 'template patterns', 'webhook verification', 'attachment handling', 'error recovery', 'sending emails via API', 'handling bounces/complaints', 'migrating between providers'. Names specific providers (Resend, SendGrid, Mailgun, SMTP2Go) with their characteristics. | 3 / 3 |
Completeness | Clearly answers both what (multi-provider email sending with specific capabilities) AND when with explicit 'Use when' clause: 'sending emails via API, handling bounces/complaints, or migrating between providers'. The trigger guidance is explicit and actionable. | 3 / 3 |
Trigger Term Quality | Excellent coverage of natural terms users would say: 'email sending', 'Cloudflare Workers', 'Node.js', 'transactional email', 'Resend', 'SendGrid', 'Mailgun', 'SMTP2Go', 'React Email', 'webhooks', 'bounces', 'complaints', 'API'. Includes both provider names and common email-related terminology. | 3 / 3 |
Distinctiveness Conflict Risk | Highly distinctive with clear niche: email sending specifically for Cloudflare Workers/Node.js with named providers. The combination of runtime environments, specific email providers, and use cases (transactional, webhooks, bounces) creates a unique fingerprint unlikely to conflict with other skills. | 3 / 3 |
Total | 12 / 12 Passed |
Implementation
64%Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.
This is a highly actionable skill with excellent executable code examples covering four email providers comprehensively. However, it suffers from being overly verbose with redundant comparison tables and inline content that would benefit from being split into separate reference files. The workflow clarity could be improved with explicit validation steps for batch operations and provider migrations.
Suggestions
Split provider-specific details (TypeScript interfaces, webhook handlers, error tables) into separate reference files like RESEND.md, SENDGRID.md, etc., keeping only quick-start examples in the main skill
Add explicit validation checkpoints for batch sending workflows (e.g., 'Verify first 10 emails succeed before processing full batch')
Consolidate the four comparison tables into a single comprehensive table or move to a COMPARISON.md reference file
Add a migration checklist with verification steps: test connectivity, send test email, verify webhook delivery, confirm analytics tracking
| Dimension | Reasoning | Score |
|---|---|---|
Conciseness | The skill is comprehensive but includes excessive comparison tables and redundant information across providers. Many sections could be consolidated, and the extensive TypeScript interfaces for all four providers add bulk that could be referenced externally. | 2 / 3 |
Actionability | Excellent executable code examples for all four providers with complete, copy-paste ready implementations. Each pattern includes full TypeScript code with proper error handling, authentication, and response parsing. | 3 / 3 |
Workflow Clarity | While individual operations are clear, the skill lacks explicit validation checkpoints for batch operations and webhook setup. The migration section provides abstraction but doesn't include verification steps to confirm successful provider switching. | 2 / 3 |
Progressive Disclosure | Content is well-organized with clear sections, but everything is inline in one massive file (~1200 lines). Advanced topics like React Email templates, webhook verification, and provider abstraction patterns should be split into separate reference files. | 2 / 3 |
Total | 9 / 12 Passed |
Validation
68%Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.
Validation — 11 / 16 Passed
Validation for skill structure
| Criteria | Description | Result |
|---|---|---|
skill_md_line_count | SKILL.md is long (1405 lines); consider splitting into references/ and linking | Warning |
metadata_version | 'metadata.version' is missing | Warning |
metadata_field | 'metadata' should map string keys to string values | Warning |
frontmatter_unknown_keys | Unknown frontmatter key(s) found; consider removing or moving to metadata | Warning |
body_steps | No step-by-step structure detected (no ordered list); consider adding a simple workflow | Warning |
Total | 11 / 16 Passed | |
- Reviewed
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