# N8n Validation Expert

Interpret validation errors and guide fixing them.

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

## Install

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

## Description

Interpret validation errors and guide fixing them. Use when encountering validation errors, validation warnings, false positives, operator structure issues, or need help understanding validation results. Also use when asking about validation profiles, error types, the validation loop process, or auto-fix capabilities. Consult this skill whenever a validate_node or validate_workflow call returns errors or warnings, it knows which warnings are false positives and which errors need real fixes.

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

# n8n Validation Expert

Expert guide for interpreting and fixing n8n validation errors.

---

## Validation Philosophy

**Validate early, validate often**

Validation is typically iterative:
- Expect validation feedback loops
- Usually 2-3 validate → fix cycles
- Average: 23s thinking about errors, 58s fixing them

**Key insight**: Validation is an iterative process, not one-shot!

---

## Error Severity Levels

### 1. Errors (Must Fix)
**Blocks workflow execution** - Must be resolved before activation

**Types**:
- `missing_required` - Required field not provided
- `invalid_value` - Value doesn't match allowed options
- `type_mismatch` - Wrong data type (string instead of number)
- `invalid_reference` - Referenced node doesn't exist
- `invalid_expression` - Expression syntax error

**Example**:
```json
{
  "type": "missing_required",
  "property": "channel",
  "message": "Channel name is required",
  "fix": "Provide a channel name (lowercase, no spaces, 1-80 characters)"
}
```

### 2. Warnings (Should Fix)
**Doesn't block execution** - Workflow can be activated but may have issues

**Types**:
- `best_practice` - Recommended but not required, surfaces under `ai-friendly` / `strict` only
- `deprecated` - Using old API/feature, surfaces under every profile
- `security` - Hardcoded secrets, unauthenticated webhooks, surfaces under every profile
- `performance` - Potential performance issue, advisory, `ai-friendly` / `strict`

**Example** (best-practice, appears under `ai-friendly` / `strict`):
```json
{
  "type": "warning",
  "nodeName": "Slack",
  "message": "Slack API can have rate limits and transient failures"
}
```

### 3. Suggestions (Optional)
**Nice to have** - Improvements that could enhance workflow

**Types**:
- `optimization` - Could be more efficient
- `alternative` - Better way to achieve same result

---

## The Validation Loop

### Pattern from Telemetry
**7,841 occurrences** of this pattern:

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