Send newsletter

Sends a newsletter now, or schedules it, to every contact with a confirmed opt-in inside its audience; unsubscribed contacts never receive it. Needs an approved template and an idempotency key. Sending cannot be undone once started.

POST /v1/newsletters/{newsletter_id}/send

Permission	`newsletters:send` (all permissions)
Risk	Send (reaches other people)
Idempotency-Key	Required (how it works)
Safe to repeat	Safe to repeat with the same Idempotency-Key: the first answer comes back and nothing is done twice.
Rate limit class	`send` (120 requests per minute per key)
Confirmation	None
MCP tool	`send_newsletter`
Since version	2026-10-25

#What it does

Sends WhatsApp messages to contacts.
Safe to repeat with the same Idempotency-Key.

#Request

Header

Name	Required	Description
`Authorization`	yes	`Bearer <key>`
`Idempotency-Key`	yes	A unique value for this operation, for example a UUID (1 to 255 visible ASCII characters).

Path parameters

Name	Type	Description
`newsletter_id`	string	ID of the newsletter, from list_newsletters.

Body (JSON)

Name	Type	Required	Description
`when`	string	yes	'now' or a time in ISO 8601, for example 2026-11-03T10:00:00+01:00. A time without a zone counts as Zurich time. length 3 to 40

#Examples

curlPythonTypeScript

curl -X POST "https://api.smartchat.marketing/v1/newsletters/nwl_3c9e1f7a5b2d4e8f9a0b1c2d3e4f5a6b/send" \
  -H "Authorization: Bearer $SMARTCHAT_API_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Content-Type: application/json" \
  -d '{
  "when": "now"
}'

import os
import uuid
import requests

response = requests.post(
    "https://api.smartchat.marketing/v1/newsletters/nwl_3c9e1f7a5b2d4e8f9a0b1c2d3e4f5a6b/send",
    headers={
        "Authorization": "Bearer " + os.environ["SMARTCHAT_API_KEY"],
        "Idempotency-Key": str(uuid.uuid4()),
    },
    json={
        "when": "now",
    },
)
response.raise_for_status()
print(response.json())

const response = await fetch("https://api.smartchat.marketing/v1/newsletters/nwl_3c9e1f7a5b2d4e8f9a0b1c2d3e4f5a6b/send", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.SMARTCHAT_API_KEY}`,
    "Idempotency-Key": crypto.randomUUID(),
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "when": "now"
  }),
});
if (!response.ok) throw new Error(await response.text());
console.log(await response.json());

Response (202):

{
  "object": "newsletter_send",
  "id": "nwl_3c9e1f7a5b2d4e8f9a0b1c2d3e4f5a6b",
  "newsletter_id": "nwl_3c9e1f7a5b2d4e8f9a0b1c2d3e4f5a6b",
  "status": "sending",
  "recipients": 412,
  "scheduled_at": null
}

#Response

Status 202. Every response has the headers Request-Id, SmartChat-Version and X-RateLimit-*.

Name	Type	Description
`object`	string	Always "newsletter_send". always `newsletter_send`
`id`	string	ID of the send. It is the newsletter ID.
`newsletter_id`	string	Newsletter ID.
`status`	string	sending = messages are queued now. scheduled = they go out at scheduled_at. one of: `sending`, `scheduled`
`recipients`	integer	Contacts that receive the newsletter. 0 to 100000000
`scheduled_at`	string or null	When the send starts if it is scheduled, otherwise null. up to 40 characters; format date-time

#Errors

Code	Status	When
`bad_request`	400	The request could not be read.
`idempotency_key_invalid`	400	The 'Idempotency-Key' header must be 1 to 255 visible ASCII characters.
`idempotency_key_required`	400	This call needs an 'Idempotency-Key' header.
`missing_parameter`	400	A required field is missing.
`unknown_parameter`	400	A field is not known.
`api_key_expired`	401	This API key has expired.
`api_key_invalid`	401	This API key is not valid.
`api_key_revoked`	401	This API key was revoked.
`authentication_required`	401	No API key was sent. Send 'Authorization: Bearer <key>'.
`insufficient_credits`	402	The credits are not enough.
`quota_exceeded`	402	The monthly message quota is used up.
`account_blocked`	403	This account is blocked.
`insufficient_scope`	403	This key lacks a required permission.
`ip_not_allowed`	403	This IP address is not allowed for this key.
`subscription_locked`	403	The subscription or payment state blocks this function.
`newsletter_not_found`	404	No newsletter with this ID exists in this account.
`conflict`	409	The state of the object does not allow this.
`idempotency_in_progress`	409	A request with this idempotency key is still running.
`newsletter_locked`	409	The newsletter is scheduled or sent and cannot be changed.
`audience_empty`	422	The audience has no reachable contacts.
`idempotency_key_reused`	422	This idempotency key was already used with a different request.
`template_not_approved`	422	The template is not approved.
`template_rejected`	422	WhatsApp rejected the template.
`validation_failed`	422	A field is not valid.
`whatsapp_not_connected`	422	No WhatsApp number is connected.
`rate_limited`	429	Too many requests. Wait and try again.
`internal_error`	500	Something went wrong on our side.
`upstream_error`	502	A connected service (for example WhatsApp) reported an error.
`service_unavailable`	503	The service is temporarily unavailable.
`suppression_check_unavailable`	503	The suppression list cannot be read, so nothing was sent.

All errors use one format.