# N8n Expression Syntax

Validate n8n expression syntax and fix common errors.

- Repository: https://github.com/czlonkowski/n8n-mcp (23187 stars)
- Category: Writing
- License: MIT
- Last updated: 2026-10-27
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add czlonkowski/n8n-mcp --skill n8n-expression-syntax -g -a claude-code -y`
Codex: `npx skills add czlonkowski/n8n-mcp --skill n8n-expression-syntax -g -a codex -y`
Cursor: `npx skills add czlonkowski/n8n-mcp --skill n8n-expression-syntax -g -a cursor -y`
Gemini CLI: `npx skills add czlonkowski/n8n-mcp --skill n8n-expression-syntax -g -a gemini-cli -y`

## Description

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.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# n8n Expression Syntax

Expert guide for writing correct n8n expressions in workflows.

---

## Expression Format

All dynamic content in n8n uses **double curly braces**:

```
{{expression}}
```

**Examples**:
```
✅ {{$json.email}}
✅ {{$json.body.name}}
✅ {{$node["HTTP Request"].json.data}}
❌ $json.email  (no braces - treated as literal text)
❌ {$json.email}  (single braces - invalid)
```

---

## Core Variables

### $json - Current Node Output

Access data from the current node:

```javascript
{{$json.fieldName}}
{{$json['field with spaces']}}
{{$json.nested.property}}
{{$json.items[0].name}}
```

### $node - Reference Other Nodes

Access data from any previous node:

```javascript
{{$node["Node Name"].json.fieldName}}
{{$node["HTTP Request"].json.data}}
{{$node["Webhook"].json.body.email}}
```

**Important**:
- Node names **must** be in quotes
- Node names are **case-sensitive**
- Must match exact node name from workflow

### $now - Current Timestamp

Access current date/time:

```javascript
{{$now}}
{{$now.toFormat('yyyy-MM-dd')}}
{{$now.toFormat('HH:mm:ss')}}
{{$now.plus({days: 7})}}
```

### $env - Environment Variables

Access environment variables:

```javascript
{{$env.API_KEY}}
{{$env.DATABASE_URL}}
```

**Warning**: Some n8n instances have `N8N_BLOCK_ENV_ACCESS_IN_NODE` enabled, which blocks `$env` access entirely. If `$env` returns errors, use alternative approaches:
- Store values in credentials instead
- Use a Set node with manually entered values
- Pass values through webhook query parameters

---

## 🚨 CRITICAL: Webhook Data Structure

**Most Common Mistake**: Webhook data is **NOT** at the root!

### Webhook Node Output Structure

```javascript
{
  "headers": {...},
  "params": {...},
  "query": {...},
  "body": {           // ⚠️ USER DATA IS HERE!
    "name": "John",
    "email": "john@example.com",
    "message": "Hello"
  }
}
```

### Correct Webhook Data Access

```javascript
❌ WRONG: {{$json.name}}
❌ WRONG: {{$json.email}}

The rest: https://github.com/czlonkowski/n8n-mcp/blob/HEAD/data/skills/n8n-expression-syntax/SKILL.md