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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. Also use when asked whether a complex expression hurts performance.

68

Quality

83%

Does it follow best practices?

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SecuritybySnyk

Passed

No findings from the security scan

SKILL.md
Quality
Evals
Security

Quality

Content

71%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 rich, highly actionable n8n expression reference with concrete examples, a strong transform decision process, and valuable debugging/performance guidance. Its main weaknesses are repeated restatement of the same core rules across sections and dangling links to bundle files (COMMON_MISTAKES.md, EXAMPLES.md) that are not present.

Suggestions

Consolidate the rules repeated across Expression Format, Validation Rules, Common Mistakes, Best Practices, and Summary ({{}} wrapping, webhook .body, no expressions in Code nodes) into one canonical section and cross-reference it instead of restating.

Create the referenced COMMON_MISTAKES.md and EXAMPLES.md files (or remove the dangling links) so progressive-disclosure references actually resolve.

Move the full error catalog and extended worked examples into those referenced files, keeping SKILL.md a lean overview with key inline snippets.

DimensionReasoningScore

Conciseness

The body is ~650 lines and restates the same rules across multiple sections — {{}} wrapping appears in Expression Format, Validation Rules, Common Mistakes, Best Practices, and Summary; webhook .body and Code-node-no-expression recur similarly — so it is mostly valuable n8n-specific content but could be tightened; not a 2 because most material is non-obvious domain knowledge rather than concepts Claude already knows.

3 / 5

Actionability

Abundant copy-paste-ready expressions with ✅/❌ pairs, a concrete IIFE-in-Edit-Fields pattern, and a precise $jmespath quoting table covering the common cases with executable syntax.

5 / 5

Workflow Clarity

The transform gatekeeper (expression → IIFE → Code node) is a clearly ordered decision process with rationale, and the debugging section has a real feedback loop (test → inspect output for null → wrap to surface the real error); not a 5 because some validation checkpoints are implicit rather than enumerated as a checklist.

4 / 5

Progressive Disclosure

Section headers give reasonable structure and references to COMMON_MISTAKES.md and EXAMPLES.md are clearly signaled as links, but neither file exists in the bundle, so the references are dangling against a 650-line monolithic body; not a 4 because the broken offload undermines the intended split.

3 / 5

Total

15

/

20

Passed

Description

95%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, well-structured description: concrete domain, comprehensive natural trigger terms, and explicit what/when guidance in third-person voice. The only weakness is modest verb breadth in the what-clause, slightly capping specificity.

DimensionReasoningScore

Specificity

"Validate n8n expression syntax and fix common errors" names the domain plus several concrete actions (validate, fix, access $json/$node, map data, reference webhook data), with only minor coverage gaps; not a 5 because the core what-clause carries just two primary verbs.

4 / 5

Completeness

Explicitly answers both what ("Validate n8n expression syntax and fix common errors") and when via multiple concrete "Use when" / "Use this skill whenever" / "Also use when" clauses with specific trigger phrases.

5 / 5

Trigger Term Quality

Comprehensive natural trigger terms including synonyms and syntax tokens — "writing n8n expressions", "using {{}} syntax", "accessing $json/$node variables", "troubleshooting expression errors", "mapping data between nodes", "referencing webhook data", and "asked whether a complex expression hurts performance".

5 / 5

Distinctiveness Conflict Risk

n8n expression syntax is a clear niche with distinct, syntax-specific triggers ({{}}, $json/$node, webhook .body) that are unlikely to fire for unrelated skills; uses third-person voice with no first/second-person penalty.

5 / 5

Total

19

/

20

Passed

Validation

87%

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 14 / 16 Passed

Validation for skill structure

CriteriaDescriptionResult

skill_md_line_count

SKILL.md is long (660 lines); consider splitting into references/ and linking

Warning

relative_links

Relative link issues: 4 missing

Warning

Total

14

/

16

Passed

Repository
czlonkowski/n8n-skills
Reviewed

Table of Contents

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