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.

Quality

80%

Does it follow best practices?

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Adds up to 20 points to the overall score

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Securityby

Passed

No findings from the security scan

Quality

Content

70%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.

Highly actionable, executable content with a strong transform-decision workflow, but it is over-long with significant repetition across sections and references two bundle files that are absent, undermining the progressive-disclosure structure.

Suggestions

Create the referenced COMMON_MISTAKES.md and EXAMPLES.md (or remove the links), so the 'one level deep' navigation resolves to real files.

Deduplicate: consolidate the repeated webhook-.body and Code-node guidance into single canonical sections and have other sections link to them instead of restating.

Tighten the Summary/Best Practices/'When NOT to Use' sections, which restate rules already covered, to reduce token cost without losing the quick-reference value.

Dimension	Reasoning	Score
Conciseness	Mostly efficient but padded: the same webhook-.body mistake and Code-node guidance are restated across 'CRITICAL: Webhook Data Structure', 'When NOT to Use Expressions', 'Common Mistakes', 'Best Practices', and 'Summary', and the same field-with-bracket-notation examples recur several times.	3 / 5
Actionability	Fully executable copy-paste expressions throughout — correct {{}} syntax, $json/$node/$now/$env usage, bracket notation, ternaries, Luxon date math, and an IIFE gatekeeper pattern — covering the common cases with concrete working examples.	5 / 5
Workflow Clarity	The 'transform gatekeeper' is a clearly sequenced decision order (Expression → IIFE → Code node) with explicit rationale, and debugging gives an error→cause→fix pattern, but the validation/error-recovery feedback loops are advisory lists rather than enforceable checkpoints, leaving minor gaps.	4 / 5
Progressive Disclosure	Structure is well sectioned and references COMMON_MISTAKES.md and EXAMPLES.md, but those referenced files do not exist in the bundle, so the navigation signals point at missing material and the inline content carries what should live in those separate files.	3 / 5
	Total	15 / 20 Passed

Description

91%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, specific description with clear 'what' and multiple explicit 'when' triggers tied to natural user language. The only minor weakness is a touch of redundancy and scenario framing rather than a clean action list, but it does not rise to a penalty.

Dimension	Reasoning	Score
Specificity	Names the domain (n8n expressions) and several concrete actions — 'Validate n8n expression syntax and fix common errors', 'accessing $json/$node variables', 'mapping data between nodes', 'referencing webhook data' — but some are framed as scenarios rather than distinct capabilities, leaving minor coverage gaps.	4 / 5
Completeness	Explicitly answers both what ('Validate n8n expression syntax and fix common errors') and when ('Use when writing n8n expressions...', 'Use this skill whenever configuring node fields that reference data from previous nodes', 'Also use when asked whether a complex expression hurts performance') with concrete trigger phrases.	5 / 5
Trigger Term Quality	Comprehensive natural trigger phrases including 'writing n8n expressions', 'using {{}} syntax', 'troubleshooting expression errors', 'mapping data between nodes', 'referencing webhook data', plus the literal variable names users would mention.	5 / 5
Distinctiveness Conflict Risk	Narrow n8n-expression niche with distinctive triggers ({{}} syntax, $json/$node variables, webhook data, node field configuration); minimal overlap risk with adjacent n8n skills since the scope is explicitly scoped to expression syntax.	5 / 5
	Total	19 / 20 Passed

Validation

87%

Warnings & errors only

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

Criteria	Description	Result
skill_md_line_count	SKILL.md is long (600 lines); consider splitting into references/ and linking	Warning
relative_links	Relative link issues: 4 missing	Warning

	Total	14 / 16 Passed

Repository: czlonkowski/n8n-skills
Path: skills/n8n-expression-syntax/SKILL.md
Commit: 0296522

Reviewed: 4 days ago

Table of Contents

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