Instagram Creator Marketplace Messaging API: the 250,000 follower cap

The Instagram Creator Marketplace Messaging API lets a brand send paid partnership messages only to creators who are onboarded to the creator marketplace, have 250,000 or fewer followers and allow message access. Sume can shortlist Instagram creators with follower_max set to 250000, but it does not know who is onboarded and does not send messages.

Instagram facts are from its Platform changelog entry of Sep 22, 2026; Sume facts from the OpenAPI document behind the API reference, read 2026-10-01.

What does the new API require?

The changelog says brands send messages through the Partnership folder on Instagram. It requires the new instagram_creator_marketplace_messaging permission and a Page access token for a Page connected to a brand that has onboarded to Instagram's creator marketplace. It is only available in the Instagram API with Facebook Login.

How do I shortlist inside the band with Sume?

POST /v1/influencer-search is a ranked cold-discovery shortlist from a niche or natural-language query. It takes follower_min, follower_max and engagement_min, and platforms accepts ig. It is unbilled, with no Sume SKU.

curl -X POST https://api.sume.com/v1/influencer-search \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "niche": "k-beauty",
    "platforms": ["ig"],
    "follower_min": 20000,
    "follower_max": 250000,
    "limit": 12
  }'

What does the shortlist not tell me?

Whether a creator is onboarded to the marketplace, or allows message access. The changelog says the marketplace discovery endpoint is GET /<IG_USER_ID>/creator_marketplace_creators, which is where eligibility is checked. Use the Sume list to decide who to look up, then let that endpoint confirm.

What about paid partnership disclosure?

Messages are one half; the post is the other. For how a sponsored post is flagged on another network, see the X paid partnership field. Follow each platform's own rules.