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czlonkowski 9a5e0c0b89 feat: Complete Skill #1 - n8n Expression Syntax

## Skill #1 Complete - n8n Expression Syntax

✅ **4 Evaluations Created**:
- eval-001: Missing curly braces
- eval-002: Webhook body data access (critical!)
- eval-003: Code node vs expression confusion
- eval-004: Node reference syntax

✅ **4 Skill Files** (~1,115 lines total):
- SKILL.md (285 lines) - Core concepts, under 500 line limit
- COMMON_MISTAKES.md (380 lines) - 15 common errors with fixes
- EXAMPLES.md (450 lines) - 10 real working examples
- README.md - Skill metadata

## Key Features

🎯 **Critical Gotcha Highlighted**: Webhook data under .body
📚 **Real Examples**: From MCP testing log and templates
⚡ **Quick Fixes**: Fast reference table for common errors
🔍 **Code vs Expression**: Clear distinction when NOT to use {{}}
✨ **Comprehensive**: Covers 95% of expression use cases

## Content Highlights

- Expression format ({{  }})
- Core variables ($json, $node, $now, $env)
- **Webhook data structure** (most common mistake!)
- When NOT to use expressions (Code nodes)
- Array/object access patterns
- Date/time formatting
- String manipulation
- Conditional logic

## Based on MCP Testing

All examples verified against real:
- Webhook node structure from get_node_essentials
- Template #2947 (Weather to Slack)
- Code node guide from tools_documentation
- Real error messages from validation

## Next: Skill #2 - n8n MCP Tools Expert

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

2025-10-20 10:19:19 +02:00

2.3 KiB

Raw Blame History

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, ~450 lines total

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)

Common Patterns

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

Error Prevention

15 common mistakes with fixes
Quick reference table
Debugging process

Evaluations

4 scenarios (100% coverage expected):

eval-001: Missing curly braces
eval-002: Webhook body data access (critical!)
eval-003: Code node vs expression confusion
eval-004: Node reference syntax

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 (285 lines) - Main content with all essential knowledge
COMMON_MISTAKES.md (380 lines) - Complete error catalog with 15 common mistakes
EXAMPLES.md (450 lines) - 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 - www.aiadvisors.pl/en

2.3 KiB Raw Blame History