n8n-skills/skills/n8n-mcp-tools-expert/VALIDATION_GUIDE.md

Configuration Validation Tools Guide

Complete guide for validating node configurations and workflows.

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Validation Philosophy

Validate early, validate often

Validation is typically iterative with validate → fix cycles

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validate_node (UNIFIED VALIDATION)

The validate_node tool provides all validation capabilities with different modes.

Quick Check (mode="minimal")

Speed: <50ms

Use when: Checking what fields are required

validate_node({
  nodeType: "nodes-base.slack",
  config: {},  // Empty to see all required fields
  mode: "minimal"
})

Returns:

{
  "valid": true,           // Usually true (most nodes have no strict requirements)
  "missingRequiredFields": []
}

When to use: Planning configuration, seeing basic requirements

Full Validation (mode="full", DEFAULT)

Speed: <100ms

Use when: Validating actual configuration before deployment

validate_node({
  nodeType: "nodes-base.slack",
  config: {
    resource: "channel",
    operation: "create",
    channel: "general"
  },
  profile: "runtime"  // Recommended!
})
// mode="full" is the default

---

Validation Profiles

Choose based on your stage:

minimal - Only required fields

• Fastest
• Most permissive
• Use: Quick checks during editing

runtime - Values + types (RECOMMENDED)

• Balanced validation
• Catches real errors
• Use: Pre-deployment validation

ai-friendly - Reduce false positives

• For AI-generated configs
• Tolerates minor issues
• Use: When AI configures nodes

strict - Maximum validation

• Strictest rules
• May have false positives
• Use: Production deployment

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Validation Response

{
  "nodeType": "nodes-base.slack",
  "workflowNodeType": "n8n-nodes-base.slack",
  "displayName": "Slack",
  "valid": false,
  "errors": [
    {
      "type": "missing_required",
      "property": "name",
      "message": "Channel name is required",
      "fix": "Provide a channel name (lowercase, no spaces, 1-80 characters)"
    }
  ],
  "warnings": [
    {
      "type": "best_practice",
      "property": "errorHandling",
      "message": "Slack API can have rate limits",
      "suggestion": "Add onError: 'continueRegularOutput' with retryOnFail"
    }
  ],
  "suggestions": [],
  "summary": {
    "hasErrors": true,
    "errorCount": 1,
    "warningCount": 1,
    "suggestionCount": 0
  }
}

Error Types

• missing_required - Must fix
• invalid_value - Must fix
• type_mismatch - Must fix
• best_practice - Should fix (warning)
• suggestion - Optional improvement

---

validate_workflow (STRUCTURE VALIDATION)

Speed: 100-500ms

Use when: Checking complete workflow before execution

Syntax:

validate_workflow({
  workflow: {
    nodes: [...],        // Array of nodes
    connections: {...}   // Connections object
  },
  options: {
    validateNodes: true,       // Default: true
    validateConnections: true, // Default: true
    validateExpressions: true, // Default: true
    profile: "runtime"         // For node validation
  }
})

Validates:

• Node configurations
• Connection validity (no broken references)
• Expression syntax ({{ }} patterns)
• Workflow structure (triggers, flow)
• AI connections (8 types)

Returns: Comprehensive validation report with errors, warnings, suggestions

Validate by Workflow ID

// Validate workflow already in n8n
n8n_validate_workflow({
  id: "workflow-id",
  options: {
    validateNodes: true,
    validateConnections: true,
    validateExpressions: true,
    profile: "runtime"
  }
})

---

Validation Loop Pattern

Typical cycle: 23s thinking, 58s fixing

1. Configure node
   ↓
2. validate_node (23s thinking about errors)
   ↓
3. Fix errors
   ↓
4. validate_node again (58s fixing)
   ↓
5. Repeat until valid

Example:

// Iteration 1
let config = {
  resource: "channel",
  operation: "create"
};

const result1 = validate_node({
  nodeType: "nodes-base.slack",
  config,
  profile: "runtime"
});
// → Error: Missing "name"

// Iteration 2 (~58s later)
config.name = "general";

const result2 = validate_node({
  nodeType: "nodes-base.slack",
  config,
  profile: "runtime"
});
// → Valid!

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Auto-Sanitization System

When it runs: On ANY workflow update (create or update_partial)

What it fixes (automatically on ALL nodes):

1. Binary operators (equals, contains, greaterThan) → removes singleValue
2. Unary operators (isEmpty, isNotEmpty, true, false) → adds singleValue: true
3. Invalid operator structures → corrects to proper format
4. IF v2.2+ nodes → adds complete conditions.options metadata
5. Switch v3.2+ nodes → adds complete conditions.options for all rules

What it CANNOT fix:

• Broken connections (references to non-existent nodes)
• Branch count mismatches (3 Switch rules but only 2 outputs)
• Paradoxical corrupt states (API returns corrupt, rejects updates)

Example:

// Before auto-sanitization
{
  "type": "boolean",
  "operation": "equals",
  "singleValue": true  // Binary operators shouldn't have this
}

// After auto-sanitization (automatic!)
{
  "type": "boolean",
  "operation": "equals"
  // singleValue removed automatically
}

Recovery tools:

• cleanStaleConnections operation - removes broken connections
• n8n_autofix_workflow({id}) - preview/apply fixes

---

n8n_autofix_workflow (AUTO-FIX TOOL)

Use when: Validation errors need automatic fixes

// Preview fixes (default - doesn't apply)
n8n_autofix_workflow({
  id: "workflow-id",
  applyFixes: false,  // Preview mode
  confidenceThreshold: "medium"  // high, medium, low
})

// Apply fixes
n8n_autofix_workflow({
  id: "workflow-id",
  applyFixes: true
})

Fix Types:

• expression-format - Fix expression syntax
• typeversion-correction - Correct typeVersion
• error-output-config - Fix error output settings
• webhook-missing-path - Add missing webhook paths
• typeversion-upgrade - Upgrade to latest version
• version-migration - Apply version migrations

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Binary vs Unary Operators

Binary operators (compare two values):

• equals, notEquals, contains, notContains
• greaterThan, lessThan, startsWith, endsWith
• Must NOT have singleValue: true

Unary operators (check single value):

• isEmpty, isNotEmpty, true, false
• Must have singleValue: true

Auto-sanitization fixes these automatically!

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Handling Validation Errors

Process

1. Read error message carefully
2. Check if it's a known false positive
3. Fix real errors
4. Validate again
5. Iterate until clean

Common Errors

"Required field missing" → Add the field with appropriate value

"Invalid value" → Check allowed values in get_node output

"Type mismatch" → Convert to correct type (string/number/boolean)

"Cannot have singleValue" → Auto-sanitization will fix on next update

"Missing operator metadata" → Auto-sanitization will fix on next update

False Positives

Some validation warnings may be acceptable:

• Optional best practices
• Node-specific edge cases
• Profile-dependent issues

Use ai-friendly profile to reduce false positives.

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Best Practices

Do

• Use runtime profile for pre-deployment
• Validate after every configuration change
• Fix errors immediately (avg 58s)
• Iterate validation loop
• Trust auto-sanitization for operator issues
• Use mode: "minimal" for quick checks
• Use n8n_autofix_workflow for bulk fixes
• Activate workflows via API when ready (activateWorkflow operation)

Don't

• Skip validation before deployment
• Ignore error messages
• Use strict profile during development (too many warnings)
• Assume validation passed (check result)
• Try to manually fix auto-sanitization issues

---

Example: Complete Validation Workflow

// Step 1: Get node requirements (quick check)
validate_node({
  nodeType: "nodes-base.slack",
  config: {},
  mode: "minimal"
});
// → Know what's required

// Step 2: Configure node
const config = {
  resource: "message",
  operation: "post",
  channel: "#general",
  text: "Hello!"
};

// Step 3: Validate configuration (full validation)
const result = validate_node({
  nodeType: "nodes-base.slack",
  config,
  profile: "runtime"
});

// Step 4: Check result
if (result.valid) {
  console.log("Configuration valid!");
} else {
  console.log("Errors:", result.errors);
  // Fix and validate again
}

// Step 5: Validate in workflow context
validate_workflow({
  workflow: {
    nodes: [{...config as node...}],
    connections: {...}
  }
});

// Step 6: Apply auto-fixes if needed
n8n_autofix_workflow({
  id: "workflow-id",
  applyFixes: true
});

---

Summary

Key Points:

1. Use runtime profile (balanced validation)
2. Validation loop: validate → fix (58s) → validate again
3. Auto-sanitization fixes operator structures automatically
4. Binary operators ≠ singleValue, Unary operators = singleValue: true
5. Iterate until validation passes
6. Use n8n_autofix_workflow for automatic fixes

Tool Selection:

• validate_node({mode: "minimal"}): Quick required fields check
• validate_node({profile: "runtime"}): Full config validation (use this!)
• validate_workflow: Complete workflow check
• n8n_validate_workflow({id}): Validate existing workflow
• n8n_autofix_workflow({id}): Auto-fix common issues

Related:

• SEARCH_GUIDE.md - Find nodes
• WORKFLOW_GUIDE.md - Build workflows