> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/czlonkowski/n8n-skills/llms.txt
> Use this file to discover all available pages before exploring further.
# Validation Expert
> Interpret and fix n8n validation errors. Covers validation loop, profiles, error catalog, auto-sanitization, and false positives.
# Validation Expert
Expert guide for interpreting and fixing n8n validation errors.
**Validate early, validate often.** Validation is iterative — expect 2–3 validate → fix cycles. The average is 23 seconds thinking about errors and 58 seconds fixing them per cycle.
## The Validation Loop
From real telemetry: **7,841 occurrences** of this exact pattern:
```text theme={null}
1. Configure node
↓
2. validate_node (23s thinking about errors)
↓
3. Read error messages carefully
↓
4. Fix errors
↓
5. validate_node again (58s fixing)
↓
6. Repeat until valid (usually 2–3 iterations)
```
### Example Loop
```javascript theme={null}
// Iteration 1
let config = {
resource: "channel",
operation: "create"
};
const result1 = validate_node({
nodeType: "nodes-base.slack",
config,
profile: "runtime"
});
// → Error: Missing "name"
// ⏱ 23 seconds thinking...
// Iteration 2
config.name = "general";
const result2 = validate_node({
nodeType: "nodes-base.slack",
config,
profile: "runtime"
});
// → Error: Missing "text"
// ⏱ 58 seconds fixing...
// Iteration 3
config.text = "Hello!";
const result3 = validate_node({
nodeType: "nodes-base.slack",
config,
profile: "runtime"
});
// → Valid! ✅
```
Multiple validation iterations are **completely normal**. Don't try to fix all errors at once — address them one at a time.
## Validation Profiles
Choose the right profile for your development stage:
**Use when:** Quick checks during active editing
**Validates:** Required fields only, basic structure
**Pros:** Fastest, most permissive
**Cons:** May miss real issues
```javascript theme={null}
validate_node({
nodeType: "nodes-base.slack",
config: {},
mode: "minimal"
})
// Returns: missingRequiredFields array
```
**Use when:** Pre-deployment validation
**Validates:** Required fields, value types, allowed values, basic dependencies
**Pros:** Balanced — catches real errors without excessive noise
**Cons:** Some edge cases missed
```javascript theme={null}
validate_node({
nodeType: "nodes-base.slack",
config: {resource: "message", operation: "post", channel: "#general", text: "Hello!"},
profile: "runtime"
})
```
**Use when:** AI-generated node configurations
**Validates:** Same as runtime but reduces false positives
**Pros:** Less noisy for AI workflows
```javascript theme={null}
validate_node({
nodeType: "nodes-base.slack",
config: {...},
profile: "ai-friendly"
})
```
**Use when:** Final check before critical production deployment
**Validates:** Everything — best practices, performance, security
**Pros:** Maximum safety
**Cons:** Many warnings; some false positives; not recommended during development
```javascript theme={null}
validate_node({
nodeType: "nodes-base.slack",
config: {...},
profile: "strict"
})
```
## Validation Result Structure
```javascript theme={null}
{
"valid": false,
"errors": [
{
"type": "missing_required",
"property": "channel",
"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": [
{
"type": "optimization",
"message": "Consider using batch operations for multiple messages"
}
],
"summary": {
"hasErrors": true,
"errorCount": 1,
"warningCount": 1,
"suggestionCount": 1
}
}
```
### Error Severity Levels
| Severity | Blocks Execution? | Action Required |
| -------------- | ----------------------------------------- | ------------------ |
| **Error** | Yes — must fix before activation | Fix immediately |
| **Warning** | No — workflow can run but may have issues | Fix for production |
| **Suggestion** | No — optional improvement | Fix if convenient |
## Common Error Catalog
**What it means:** A field that is required for the selected operation is absent.
**How to fix:**
1. Use `get_node` to see what fields the operation requires
2. Add the missing field with an appropriate value
```javascript theme={null}
// Error
{
"type": "missing_required",
"property": "channel",
"message": "Channel name is required",
"fix": "Provide a channel name"
}
// Fix
config.channel = "#general";
```
**What it means:** The value provided doesn't match the list of allowed options.
**How to fix:**
1. Read the error message for the allowed values list
2. Use `get_node` to see all options
```javascript theme={null}
// Error
{
"type": "invalid_value",
"property": "operation",
"message": "Operation must be one of: post, update, delete",
"current": "send"
}
// Fix
config.operation = "post"; // Use a valid operation
```
**What it means:** The value is the right field but the wrong type (e.g., string instead of number).
```javascript theme={null}
// Error
{
"type": "type_mismatch",
"property": "limit",
"message": "Expected number, got string",
"current": "100"
}
// Fix
config.limit = 100; // Number, not string
```
**What it means:** An expression field has invalid `{{}}` syntax.
```javascript theme={null}
// Error
{
"type": "invalid_expression",
"property": "text",
"message": "Invalid expression: $json.name",
"current": "$json.name"
}
// Fix — add {{}} wrapper
config.text = "={{$json.name}}";
```
See the [Expression Syntax](/skills/expression-syntax) skill for the full expression guide.
**What it means:** An expression references a node that doesn't exist in the workflow.
```javascript theme={null}
// Error
{
"type": "invalid_reference",
"property": "expression",
"message": "Node 'HTTP Requets' does not exist",
"current": "={{$node['HTTP Requets'].json.data}}"
}
// Fix — correct the typo
config.expression = "={{$node['HTTP Request'].json.data}}";
```
## Auto-Sanitization System
Auto-sanitization runs automatically on **ALL nodes** during **ANY workflow update** (create or update\_partial).
### What It Fixes Automatically
Operators that compare two values: `equals`, `notEquals`, `contains`, `notContains`, `greaterThan`, `lessThan`, `startsWith`, `endsWith`
**Fix:** Removes `singleValue` property (binary operators should not have it)
```javascript theme={null}
// Before (wrong)
{
"type": "boolean",
"operation": "equals",
"singleValue": true // ❌ Binary operators don't need this
}
// After (auto-fixed)
{
"type": "boolean",
"operation": "equals"
// singleValue removed ✅
}
```
Operators that check a single value: `isEmpty`, `isNotEmpty`, `true`, `false`
**Fix:** Adds `singleValue: true` (unary operators require it)
```javascript theme={null}
// Before (wrong)
{
"type": "boolean",
"operation": "isEmpty"
// Missing singleValue ❌
}
// After (auto-fixed)
{
"type": "boolean",
"operation": "isEmpty",
"singleValue": true // ✅ Added automatically
}
```
**Fix:** Adds complete `conditions.options` metadata for:
* IF node v2.2+
* Switch node v3.2+
This happens automatically on save — no manual intervention needed.
### What Auto-Sanitization Cannot Fix
| Issue | Cause | Solution |
| -------------------------- | ------------------------------------- | ---------------------------------------- |
| Broken connections | References to deleted nodes | Use `cleanStaleConnections` operation |
| Branch count mismatches | 3 Switch rules but only 2 connections | Add missing connections or remove rules |
| Paradoxical corrupt states | API returns corrupt, rejects updates | May require manual database intervention |
### Auto-Fix Tool
For bulk fixes beyond auto-sanitization:
```javascript theme={null}
// Preview fixes first (default: doesn't apply)
n8n_autofix_workflow({
id: "workflow-id",
applyFixes: false,
confidenceThreshold: "medium" // high, medium, low
})
// Apply fixes after review
n8n_autofix_workflow({
id: "workflow-id",
applyFixes: true
})
```
**Fix types the auto-fix tool handles:**
* `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
## False Positives Guide
Some validation warnings are technically "wrong" but acceptable in context.
**When it's a false positive:** Simple workflows where failures are obvious, testing or development workflows, and non-critical notification workflows.
**When you should fix it:** Production workflows handling important data or payments.
**When it's a false positive:** APIs with their own built-in retry logic, idempotent operations where double-execution is harmless, and manual trigger workflows run by a human.
**When you should fix it:** Flaky external services in production automation.
**When it's a false positive:** Internal APIs with no rate limits, low-volume workflows (few executions per day), and APIs that enforce rate limiting server-side.
**When you should fix it:** Public APIs with strict rate limits and high-volume automated workflows.
**When it's a false positive:** Small, known-size datasets, aggregation queries (COUNT, SUM) that scan the full table by design, and development/testing environments.
**When you should fix it:** Production queries on large tables.
**To reduce false positives in AI-generated configurations:**
```javascript theme={null}
validate_node({
nodeType: "nodes-base.slack",
config: {...},
profile: "ai-friendly" // Fewer false positives
})
```
## Workflow Validation
```javascript theme={null}
// Validate the full workflow structure
validate_workflow({
workflow: {
nodes: [...],
connections: {...}
},
options: {
validateNodes: true,
validateConnections: true,
validateExpressions: true,
profile: "runtime"
}
})
// Validate by workflow ID (requires n8n API)
n8n_validate_workflow({
id: "workflow-id",
options: {profile: "runtime"}
})
```
### Common Workflow-Level Errors
| Error | Cause | Fix |
| ---------------------------------------------------- | ---------------------------------- | ------------------------------------------------------ |
| `Connection from 'X' to 'Y' - target node not found` | Stale connection to a deleted node | Use `cleanStaleConnections` operation |
| `Circular dependency detected: A → B → A` | Loop in workflow | Restructure to remove the cycle |
| `Multiple trigger nodes found` | More than one trigger | Remove extra triggers or split into separate workflows |
| `Node 'X' is not connected to workflow flow` | Orphaned node | Connect it or delete it |
## Recovery Strategies
**When:** Configuration is severely broken or corrupted.
```javascript theme={null}
// 1. Get required fields
get_node({nodeType: "nodes-base.slack", mode: "minimal"})
// 2. Create minimal valid config
const config = {resource: "message", operation: "post", channel: "#general", text: "Hi"};
// 3. Validate
validate_node({nodeType: "nodes-base.slack", config, profile: "runtime"})
// 4. Add features incrementally, validating after each addition
```
**When:** Seeing "Node not found" or broken connection errors.
```javascript theme={null}
n8n_update_partial_workflow({
id: "workflow-id",
intent: "Clean up stale connections after node deletions",
operations: [{type: "cleanStaleConnections"}]
})
```
**When:** Operator structure errors (isEmpty missing singleValue, etc.).
```javascript theme={null}
// Preview first
n8n_autofix_workflow({id: "workflow-id", applyFixes: false})
// Apply after review
n8n_autofix_workflow({id: "workflow-id", applyFixes: true})
```
**When:** Workflow validates but executes incorrectly and you can't pinpoint the cause.
1. Remove half the nodes
2. Validate and test
3. If it works: the problem is in the removed nodes
4. If it fails: the problem is in the remaining nodes
5. Repeat until the problem is isolated
## Profile Selection by Stage
| Development Stage | Recommended Profile |
| ------------------------------ | ------------------- |
| Initial editing / exploration | `minimal` |
| Active development | `runtime` |
| AI-generated configs | `ai-friendly` |
| Pre-deployment check | `runtime` |
| Critical production deployment | `strict` |
## Best Practices
* Validate after every significant change
* Read error messages completely before fixing
* Fix errors one at a time iteratively
* Check the `valid` field — don't assume it passed
* Trust auto-sanitization for operator issues
* Use `get_node` when the required fields aren't obvious
* Skip validation before activation
* Try to fix all errors simultaneously
* Use `strict` profile during development
* Manually fix auto-sanitization issues
* Deploy with unresolved `error` severity issues
* Ignore all warnings (some are genuinely important)