n8n-expression-syntax
Validate n8n expression syntax and fix common errors. Use when writing n8n expressions, using {{}} syntax, accessing $json/$node variables, troubleshooting expression errors, mapping data between nodes, or referencing webhook data in workflows. Use this skill whenever configuring node fields that reference data from previous nodes — expressions are how n8n passes data between nodes, and getting the syntax wrong is the most common source of workflow errors.
60
70%
Does it follow best practices?
Impact
—
No eval scenarios have been run
Advisory
Suggest reviewing before use
Optimize this skill with Tessl
npx tessl skill review --optimize ./skills/n8n-expression-syntax/SKILL.mdQuality
Discovery
89%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 a strong skill description with excellent trigger term coverage and completeness. It clearly identifies both what the skill does and when to use it, with highly specific n8n-related terminology that minimizes conflict risk. The main weakness is that the 'what' portion could enumerate more specific concrete actions beyond 'validate' and 'fix common errors'.
Suggestions
Expand the capability list with more specific actions, e.g., 'Validate n8n expression syntax, fix bracket/quoting errors, resolve $json/$node variable references, correct data mapping paths between nodes.'
| Dimension | Reasoning | Score |
|---|---|---|
Specificity | The description names the domain (n8n expression syntax) and some actions ('validate', 'fix common errors'), but doesn't list multiple specific concrete actions like parsing specific expression patterns, correcting bracket mismatches, or resolving variable reference errors. It's more about the domain than enumerating distinct capabilities. | 2 / 3 |
Completeness | Clearly answers both 'what' (validate n8n expression syntax and fix common errors) and 'when' with an explicit 'Use when...' clause covering multiple trigger scenarios, plus additional context about why this skill matters ('expressions are how n8n passes data between nodes'). | 3 / 3 |
Trigger Term Quality | Excellent coverage of natural trigger terms users would actually say: 'n8n expressions', '{{}} syntax', '$json/$node variables', 'expression errors', 'mapping data between nodes', 'webhook data', 'node fields', 'workflow errors'. These are highly specific terms an n8n user would naturally use. | 3 / 3 |
Distinctiveness Conflict Risk | Highly distinctive with a clear niche — n8n expression syntax specifically. The trigger terms like '{{}} syntax', '$json/$node variables', and 'n8n expressions' are very specific and unlikely to conflict with other skills. | 3 / 3 |
Total | 11 / 12 Passed |
Implementation
50%Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.
The skill is highly actionable with excellent concrete examples and clear correct/incorrect patterns, making it genuinely useful for n8n expression writing. However, it suffers from severe verbosity and redundancy — the same rules (especially webhook .body access and {{ }} wrapping) are repeated many times across sections, and large portions cover JavaScript basics Claude already knows. The content would benefit greatly from aggressive deduplication and offloading detailed reference material to the referenced bundle files.
Suggestions
Eliminate redundancy by stating each rule once — the webhook .body rule, {{ }} requirement, and Code node warning each appear 3-5 times across sections. Consolidate into a single authoritative section per rule.
Move Data Type Handling, Expression Helpers, Advanced Patterns, and String/Date Manipulation sections to a separate REFERENCE.md file, keeping SKILL.md as a focused overview under 150 lines.
Remove the Best Practices and Summary sections entirely — they duplicate content already covered in Validation Rules and throughout the document.
Add an explicit debugging workflow with feedback loop: 1. Write expression → 2. Test in expression editor → 3. If error, check Common Mistakes table → 4. Fix and re-test → 5. Only proceed when preview shows expected output.
| Dimension | Reasoning | Score |
|---|---|---|
Conciseness | The skill is extremely verbose at ~400+ lines with significant redundancy. The webhook data structure warning is repeated at least 4 times, the '{{ }}' rule is stated 5+ times, and the summary section rehashes everything already covered. The 'Best Practices' section entirely duplicates earlier content. Many sections (Expression Helpers, Data Type Handling) explain things Claude already knows about JavaScript. The 'Related Skills' section adds no actionable value. | 1 / 3 |
Actionability | The skill provides concrete, copy-paste ready expressions with clear correct/incorrect examples throughout. Every pattern includes executable syntax with realistic data structures, and the quick-fix table provides immediate remediation for common errors. | 3 / 3 |
Workflow Clarity | The debugging section provides a basic sequence (open editor → preview → check errors), and validation rules are clearly listed. However, there's no explicit validation workflow for writing expressions — no 'write → test → verify → fix' feedback loop. For a skill focused on fixing expression errors, the absence of a structured troubleshooting workflow with checkpoints is a gap. | 2 / 3 |
Progressive Disclosure | References to COMMON_MISTAKES.md and EXAMPLES.md are well-signaled and one level deep, which is good. However, the main file contains far too much inline content that should be in those referenced files — the working examples, data type handling, advanced patterns, and expression helpers sections could all be offloaded, making the SKILL.md a leaner overview. No bundle files were provided to verify the referenced files exist. | 2 / 3 |
Total | 8 / 12 Passed |
Validation
90%Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.
Validation — 10 / 11 Passed
Validation for skill structure
| Criteria | Description | Result |
|---|---|---|
skill_md_line_count | SKILL.md is long (526 lines); consider splitting into references/ and linking | Warning |
Total | 10 / 11 Passed | |
- Repository
- czlonkowski/n8n-skills
- Commit
27e9d0a
- Reviewed
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