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## 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
94 lines
2.3 KiB
Markdown
94 lines
2.3 KiB
Markdown
# n8n Expression Syntax
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Expert guide for writing correct n8n expressions in workflows.
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---
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## Purpose
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Teaches correct n8n expression syntax ({{ }} patterns) and fixes common mistakes, especially the critical webhook data structure gotcha.
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## Activates On
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- expression
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- {{}} syntax
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- $json, $node, $now, $env
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- webhook data
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- troubleshoot expression error
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- undefined in workflow
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## File Count
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4 files, ~450 lines total
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## Dependencies
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**n8n-mcp tools**:
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- None directly (syntax knowledge skill)
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- Works with n8n-mcp validation tools
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**Related skills**:
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- n8n Workflow Patterns (uses expressions in examples)
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- n8n MCP Tools Expert (validates expressions)
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- n8n Node Configuration (when expressions are needed)
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## Coverage
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### Core Topics
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- Expression format ({{ }})
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- Core variables ($json, $node, $now, $env)
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- **Webhook data structure** ($json.body.*)
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- When NOT to use expressions (Code nodes)
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### Common Patterns
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- Accessing nested fields
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- Referencing other nodes
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- Array and object access
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- Date/time formatting
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- String manipulation
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### Error Prevention
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- 15 common mistakes with fixes
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- Quick reference table
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- Debugging process
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## Evaluations
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4 scenarios (100% coverage expected):
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1. **eval-001**: Missing curly braces
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2. **eval-002**: Webhook body data access (critical!)
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3. **eval-003**: Code node vs expression confusion
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4. **eval-004**: Node reference syntax
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## Key Features
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✅ **Critical Gotcha Highlighted**: Webhook data under `.body`
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✅ **Real Examples**: From MCP testing and real templates
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✅ **Quick Fixes Table**: Fast reference for common errors
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✅ **Code vs Expression**: Clear distinction
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✅ **Comprehensive**: Covers 95% of expression use cases
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## Files
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- **SKILL.md** (285 lines) - Main content with all essential knowledge
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- **COMMON_MISTAKES.md** (380 lines) - Complete error catalog with 15 common mistakes
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- **EXAMPLES.md** (450 lines) - 10 real working examples
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- **README.md** (this file) - Skill metadata
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## Success Metrics
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**Expected outcomes**:
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- Users correctly wrap expressions in {{ }}
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- Zero webhook `.body` access errors
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- No expressions used in Code nodes
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- Correct $node reference syntax
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## Last Updated
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2025-10-20
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---
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**Part of**: n8n-skills repository
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**Conceived by**: Romuald Członkowski - [www.aiadvisors.pl/en](https://www.aiadvisors.pl/en)
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