n8n-expression-syntax_skill

Overview

This skill validates n8n expression syntax and repairs common expression errors to keep workflows running reliably. It focuses on correct use of {{}} expressions, correct access to $json, $node, $now and $env variables, and common webhook pitfalls. The goal is fast, actionable fixes and clear examples you can apply in the editor.

How this skill works

It inspects expressions for missing or extra curly braces, incorrect node or field access (including case and quoting issues), and improper usage contexts such as Code nodes, webhook paths, or credential fields. It flags webhook data access mistakes (data lives under .body), suggests bracket notation for spaces, and offers corrections and working alternatives you can paste back into n8n. Live expression editor testing steps and common error message explanations are included for debugging.

When to use it

• While authoring or reviewing expression fields that use {{...}}
• When referencing data from other nodes via $node or current output via $json
• When troubleshooting expression errors like undefined properties or literal text
• When handling webhook payloads to ensure you access .body correctly
• Before moving expressions into Code nodes, webhook paths, or credentials

Best practices

• Always wrap dynamic content in double curly braces: {{$json.field}}
• Use {{$node["Node Name"].json.field}} and quote node names with spaces
• Access webhook payloads under {{$json.body.<field>}} rather than root
• Do not use {{}} expressions inside Code nodes—use direct JavaScript variables
• Test expressions in the expression editor and fix red-highlighted errors

Example use cases

• Formatting webhook form submissions for Slack: use {{$json.body.name}} and {{$json.body.message}}
• Pulling API response data from an HTTP Request node: {{$node["HTTP Request"].json.data.items[0].name}}
• Creating date-based filenames with {{$now.toFormat('yyyy-MM-dd')}}
• Applying conditional content: {{$json.status === 'active' ? 'Active' : 'Inactive'}}
• Safely accessing fields with spaces: {{$json['user data']['first name']}}