Contacts & lists - InstantCampaign

A contact belongs to one workspace and is unique by email. Emails are trimmed and lower-cased before use. Lists are subscription lists, and a contact can be on many of them.

Endpoint	Scope	What it does
`GET /v1/contacts`	`contacts:read`	Page through contacts, newest first. Filter by `status` or `listId`.
`POST /v1/contacts`	`contacts:write`	Create or update a contact (upsert on email)
`GET /v1/contacts/search?email=`	`contacts:read`	One contact with custom field values and lists, or `null`
`GET /v1/lists`	`contacts:read`	Every list with its membership count
`POST /v1/lists/{id}/subscribe`	`contacts:write`	Add a contact to a list, creating the contact if needed
`POST /v1/lists/{id}/unsubscribe`	`contacts:write`	Remove a contact from a list

Upserting a contact

curl -X POST https://instantcampaign.ai/api/v1/contacts \
  -H "Authorization: Bearer ic_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "jane@example.com",
    "firstName": "Jane",
    "country": "GB",
    "language": "en",
    "customFields": { "plan": "pro" }
  }'

The response is 201 with created: true for a new contact and 200 with created: false for an update. Any field you leave out is left as it is.

Subscription status is never changed by an upsert. Use the list endpoints for membership.
customFields are written only for keys defined under Settings → Custom Fields. Unknown keys are ignored without an error.
source and metadata are written only when the contact is created.
When the plan’s contact limit is reached, creating a new contact answers 403 with code: "contact_limit_reached". Updating an existing contact still works.

List membership

POST /v1/lists/{id}/subscribe creates the contact if it does not exist, with status ACTIVE and source api. It then makes the membership ACTIVE, and a membership that was unsubscribed becomes active again. The call also fires the CONTACT_ADDED_TO_LIST webhook and starts journeys that trigger on joining the list.

This endpoint sends no double opt-in confirmation, whatever the list’s double opt-in setting. Subscribing someone here is a statement that you already have their consent.

POST /v1/lists/{id}/unsubscribe marks the membership UNSUBSCRIBED (it isn’t deleted, so the opt-out is remembered). The contact and its other lists are untouched. removed: false means there was nothing to unsubscribe. contactCount on GET /v1/lists counts every membership on the list, including pending and unsubscribed ones.