Fixing Meta Ads Error: “Unexpected key is_defaulting_eligible on param creative_sourcing_spec['site_links_spec'][0] (#100)”

Unexpected key is_defaulting_eligible on param creative_sourcing_spec['site_links_spec'][0] (#100)

If you're running ads in Meta Ads Manager and suddenly encounter this technical error, it can disrupt your campaign launch and waste valuable time. This issue usually appears at the ad level, particularly when working with advanced creatives, dynamic formats, or API-based ad setups.

Let’s break it down in a simple, practical way and fix it fast.

What This Error Means

Error Message:

Unexpected key is_defaulting_eligible on param creative_sourcing_spec['site_links_spec'][0] (#100)

Simple Explanation:

Meta is telling you:

• You are sending a parameter (is_defaulting_eligible)
• Inside the site links (sitelink extensions)
• But Meta does NOT recognize or allow this field

In short:
You are passing an invalid or unsupported field in your ad creative setup.

Why This Happens

This error usually occurs due to one of the following:

1. API or Automation Tools Issue

If you're using:

• Meta Marketing API
• Automation tools (Zapier, LeadsBridge, custom scripts)
• Bulk upload systems

They might include deprecated or internal fields like:
is_defaulting_eligible

2. Old Saved Ad / Template

Duplicating older ads

Using saved creatives

Sometimes hidden parameters remain in the backend.

3. Dynamic Creative or Advantage+ Setup

Meta sometimes auto-generates fields for:

• Site links
• Creative enhancements

These can conflict with manual edits.

4. Third-Party Ad Tools

Tools like:

• Shopify apps
• CRM integrations
• Ad automation dashboards

May inject unsupported fields into the payload.

How to Fix This Error

Method 1: Recreate the Ad (Best Fix)

Go to Ad Level

Click Duplicate

Create a fresh ad

Manually re-enter:

• Primary text
• Headline
• Links

Avoid reusing the problematic creative

Method 2: Remove Site Links (Temporarily)

• Go to Ad Creative
• Remove: Site links / callout extensions
• Publish again

If it works -> problem is inside sitelink config

Method 3: Check API Payload (For Developers)

If you're using API:

• Look for:

"is_defaulting_eligible": true

Remove this field completely from:

creative_sourcing_spec.site_links_spec

Method 4: Turn Off Advantage Creative

Disable:

Advantage+ Creative

Auto enhancements

Then recreate the ad

Method 5: Clear Draft & Cache

Delete the draft ad

Refresh Ads Manager

Rebuild from scratch

Method 6: Avoid Old Templates

Don’t reuse:

Old campaigns

Imported creatives

Always build fresh structure

Pro Tips (Avoid Future Errors)

• Always use latest API version
• Avoid unknown fields in payload
• Test ads in small batches first
• Use Meta Ads Manager (UI) if unsure
• Keep integrations updated

Real-World Scenario

A digital marketing agency running performance campaigns via API faced this exact issue.

Cause: Their automation tool added is_defaulting_eligible inside sitelinks

Fix: Removed the field + recreated ads

Result: Campaign approved instantly

People Also Ask

What is error code #100 in Meta Ads?

It’s a parameter validation error, meaning something in your request is invalid or unsupported.

Can I ignore this error?

No. Your ad will not publish until it's fixed.

Does this happen in Ads Manager UI?

Rarely. Mostly happens in:

API

Automation tools

Imported creatives

Is this related to Facebook policy violation?

No. This is a technical error, not a policy issue.

How do I debug Meta Ads errors faster?

Use Ads Manager preview

Check API logs

Remove custom fields one by one

Conclusion

The error “Unexpected key is_defaulting_eligible” is a technical misconfiguration, not a serious issue—but it can block your campaigns completely.

The fastest fix:
Recreate the ad and avoid unsupported parameters

If you're running large-scale campaigns or automation, make sure your system is clean, updated, and aligned with Meta’s latest API standards.