version unknown

n8n-expression-syntax

@czlonkowski⭐ 6.3k stars

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.

Choose how to use this skill

You do not need every option. Choose the path your AI client supports. The stable page stays the same; versioned files are immutable.

1. Native installer

This listing has no registered native installer command. Use the complete package or source fallback below, depending on what your client supports.

Do not guess an installer command or replace an existing version without reviewing the diff.

2. Complete package recommended

Download the ZIP when available. It includes SKILL.md plus the references, security notes and version metadata.

No complete ProSkills package is published for this listing yet.

3. Prompt-only

Copy the prompt above when the agent can read the stable page or when you want to adopt the workflow without installing a skill.

Need only the instruction file?

Download SKILL.md only if your client requires a single file. The complete ZIP is safer for a full installation because it preserves the references and release context.

No path installs or executes anything by itself. Your agent still needs access to the project files. Before updating, compare the installed version and review the diff.

7.9/10
Verified
Oct 11, 2026

// RATINGS

⭐GitHub Stars
⭐⭐⭐⭐⭐ 6.3k on GitHubGitHub ↗

Very popular

🟢ProSkills ScoreAI Verified
7.9/10
📍

Not yet listed on ClawHub or SkillsMP

// README

n8n Expression Syntax

Expert guide for writing correct n8n expressions in workflows.

Purpose

Teaches correct n8n expression syntax ({{ }} patterns) and fixes common mistakes, especially the critical webhook data structure gotcha.

Activates On

  • expression
  • {{}} syntax
  • $json, $node, $now, $env
  • webhook data
  • troubleshoot expression error
  • undefined in workflow

File Count

4 files

Dependencies

n8n-mcp tools:

  • None directly (syntax knowledge skill)
  • Works with n8n-mcp validation tools

Related skills:

  • n8n Workflow Patterns (uses expressions in examples)
  • n8n MCP Tools Expert (validates expressions)
  • n8n Node Configuration (when expressions are needed)

Coverage

Core Topics

  • Expression format ({{ }})
  • Core variables ($json, $node, $now, $env)
  • Webhook data structure ($json.body.*)
  • When NOT to use expressions (Code nodes)
  • $jmespath(object, query) — querying nested JSON in one expression, with the quoting rules that fail silently
  • Runtime errors inside {{ }} resolve to null (node still succeeds) — how to surface them

Common Patterns

  • Accessing nested fields
  • Referencing other nodes
  • Array and object access
  • Date/time formatting
  • String manipulation

Error Prevention

  • 17 common mistakes with fixes (incl. JMESPath quoting and the silent-null runtime error)
  • Quick reference table
  • Debugging process

Evaluations

6 scenarios (100% coverage expected):

  1. eval-001: Missing curly braces
  2. eval-002: Webhook body data access (critical!)
  3. eval-003: Code node vs expression confusion
  4. eval-004: Node reference syntax
  5. eval-005: $jmespath quoting (double-quoted string, bare number)
  6. eval-006: Filter drops everything on a green run (silent null)

Key Features

✅ Critical Gotcha Highlighted: Webhook data under .body ✅ Real Examples: From MCP testing and real templates ✅ Quick Fixes Table: Fast reference for common errors ✅ Code vs Expression: Clear distinction ✅ Comprehensive: Covers 95% of expression use cases

Files

  • SKILL.md - Main content with all essential knowledge
  • COMMON_MISTAKES.md - Complete error catalog with 15 common mistakes
  • EXAMPLES.md - 10 real working examples
  • README.md (this file) - Skill metadata

Success Metrics

Expected outcomes:

  • Users correctly wrap expressions in {{ }}
  • Zero webhook .body access errors
  • No expressions used in Code nodes
  • Correct $node reference syntax

Last Updated

2025-10-20

Part of: n8n-skills repository Conceived by: Romuald Członkowski - aiadvisors.pl/en

// HOW IT'S BUILT

KEY FILES

skills/n8n-expression-syntax/SKILL.mdREADME.md

// REPO STATS

6.3k stars

// SHARE

Share on XShare on LinkedIn