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:

2. Warnings (Should Fix)

Doesn't block execution - Workflow can be activated but may have issues

Types:

• best_practice - Recommended but not required
• deprecated - Using old API/feature
• performance - Potential performance issue

Example:

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:

Example

This is normal! Don't be discouraged by multiple iterations.

Validation Profiles

Choose the right profile for your stage:

minimal

Use when: Quick checks during editing

Validates:

• Only required fields
• Basic structure

Pros: Fastest, most permissive Cons: May miss issues

runtime (RECOMMENDED)

Use when: Pre-deployment validation

Validates:

• Required fields
• Value types
• Allowed values
• Basic dependencies

Pros: Balanced, catches real errors Cons: Some edge cases missed

This is the recommended profile for most use cases

ai-friendly

Use when: AI-generated configurations

Validates:

• Same as runtime
• Reduces false positives
• More tolerant of minor issues

Pros: Less noisy for AI workflows Cons: May allow some questionable configs

strict

Use when: Production deployment, critical workflows

Validates:

• Everything
• Best practices
• Performance concerns
• Security issues

Pros: Maximum safety Cons: Many warnings, some false positives

Common Error Types

1. missing_required

What it means: A required field is not provided

How to fix:

1. Use get_node to see required fields
2. Add the missing field to your configuration
3. Provide an appropriate value

Example:

2. invalid_value

What it means: Value doesn't match allowed options

How to fix:

1. Check error message for allowed values
2. Use get_node to see options
3. Update to a valid value

Example:

3. type_mismatch

What it means: Wrong data type for field

How to fix:

1. Check expected type in error message
2. Convert value to correct type

Example:

4. invalid_expression

What it means: Expression syntax error

How to fix:

1. Use n8n Expression Syntax skill
2. Check for missing {{}} or typos
3. Verify node/field references

Example:

5. invalid_reference

What it means: Referenced node doesn't exist

How to fix:

1. Check node name spelling
2. Verify node exists in workflow
3. Update reference to correct name

Example:

Auto-Sanitization System

What It Does

Automatically fixes common operator structure issues on ANY workflow update

Runs when:

• n8n_create_workflow
• n8n_update_partial_workflow
• Any workflow save operation

What It Fixes

1. Binary Operators (Two Values)

Operators: equals, notEquals, contains, notContains, greaterThan, lessThan, startsWith, endsWith

Fix: Removes singleValue property (binary operators compare two values)

Before:

After (automatic):

2. Unary Operators (One Value)

Operators: isEmpty, isNotEmpty, true, false

Fix: Adds singleValue: true (unary operators check single value)

Before:

After (automatic):

3. IF/Switch Metadata

Fix: Adds complete conditions.options metadata for IF v2.2+ and Switch v3.2+

What It CANNOT Fix

1. Broken Connections

References to non-existent nodes

Solution: Use cleanStaleConnections operation in n8n_update_partial_workflow

2. Branch Count Mismatches

3 Switch rules but only 2 output connections

Solution: Add missing connections or remove extra rules

3. Paradoxical Corrupt States

API returns corrupt data but rejects updates

Solution: May require manual database intervention

False Positives

What Are They?

Validation warnings that are technically "wrong" but acceptable in your use case

Common False Positives

1. "Missing error handling"

Warning: No error handling configured

When acceptable:

• Simple workflows where failures are obvious
• Testing/development workflows
• Non-critical notifications

When to fix: Production workflows handling important data

2. "No retry logic"

Warning: Node doesn't retry on failure

When acceptable:

• APIs with their own retry logic
• Idempotent operations
• Manual trigger workflows

When to fix: Flaky external services, production automation

3. "Missing rate limiting"

Warning: No rate limiting for API calls

When acceptable:

• Internal APIs with no limits
• Low-volume workflows
• APIs with server-side rate limiting

When to fix: Public APIs, high-volume workflows

4. "Unbounded query"

Warning: SELECT without LIMIT

When acceptable:

• Small known datasets
• Aggregation queries
• Development/testing

When to fix: Production queries on large tables

Reducing False Positives

Use ai-friendly profile:

Validation Result Structure

Complete Response

How to Read It

1. Check valid field

2. Fix errors first

3. Review warnings

4. Consider suggestions

Workflow Validation

validate_workflow (Structure)

Validates entire workflow, not just individual nodes

Checks:

1. Node configurations - Each node valid
2. Connections - No broken references
3. Expressions - Syntax and references valid
4. Flow - Logical workflow structure

Example:

Common Workflow Errors

1. Broken Connections

Fix: Remove stale connection or create missing node

2. Circular Dependencies

Fix: Restructure workflow to remove loop

3. Multiple Start Nodes

Fix: Remove extra triggers or split into separate workflows

4. Disconnected Nodes

Fix: Connect node or remove if unused

Recovery Strategies

Strategy 1: Start Fresh

When: Configuration is severely broken

Steps:

1. Note required fields from get_node
2. Create minimal valid configuration
3. Add features incrementally
4. Validate after each addition

Strategy 2: Binary Search

When: Workflow validates but executes incorrectly

Steps:

1. Remove half the nodes
2. Validate and test
3. If works: problem is in removed nodes
4. If fails: problem is in remaining nodes
5. Repeat until problem isolated

Strategy 3: Clean Stale Connections

When: "Node not found" errors

Steps:

Strategy 4: Use Auto-fix

When: Operator structure errors

Steps:

Best Practices

✅ Do

• Validate after every significant change
• Read error messages completely
• Fix errors iteratively (one at a time)
• Use runtime profile for pre-deployment
• Check valid field before assuming success
• Trust auto-sanitization for operator issues
• Use get_node when unclear about requirements
• Document false positives you accept

❌ Don't

• Skip validation before activation
• Try to fix all errors at once
• Ignore error messages
• Use strict profile during development (too noisy)
• Assume validation passed (always check result)
• Manually fix auto-sanitization issues
• Deploy with unresolved errors
• Ignore all warnings (some are important!)

Detailed Guides

For comprehensive error catalogs and false positive examples:

• ERROR_CATALOG.md - Complete list of error types with examples
• FALSE_POSITIVES.md - When warnings are acceptable

Summary

Key Points:

1. Validation is iterative (avg 2-3 cycles, 23s + 58s)
2. Errors must be fixed, warnings are optional
3. Auto-sanitization fixes operator structures automatically
4. Use runtime profile for balanced validation
5. False positives exist - learn to recognize them
6. Read error messages - they contain fix guidance

Validation Process:

1. Validate → Read errors → Fix → Validate again
2. Repeat until valid (usually 2-3 iterations)
3. Review warnings and decide if acceptable
4. Deploy with confidence

Related Skills:

• n8n MCP Tools Expert - Use validation tools correctly
• n8n Expression Syntax - Fix expression errors
• n8n Node Configuration - Understand required fields