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Documentation Index

Fetch the complete documentation index at: https://docs.nixflex.com/llms.txt

Use this file to discover all available pages before exploring further.

SMS campaigns let you send the same message (or templated variations) to many recipients in one API call. Useful for promotions, appointment batches, announcements, and follow-up sequences.

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Create a campaign

curl -X POST https://api.nixflex.com/v1/sms/campaigns \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "agent_id": "agent_125207e452f8714a",
    "from_number": "+447446466847",
    "name": "March promotion",
    "body": "Hi! Acme Dental is offering 20% off cleanings this month. Reply YES to book.",
    "recipients": [
      { "phone_number": "+447111000001" },
      { "phone_number": "+447111000002" },
      { "phone_number": "+447111000003" }
    ],
    "context_prompt": "The campaign is a 20% off cleaning promotion in March. If caller says YES, book them in for any weekday next week 9am-5pm. If NO or STOP, just thank them.",
    "schedule_type": "now"
  }'
Response: 
{
  "campaign_id": "smsc_a1b2c3d4",
  "status": "running",
  "recipients_count": 3,
  "sent_count": 0
}
The engine queues all the sends and processes them respecting your Twilio rate limit.

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Scheduling

Send later instead of now: 
{
  "schedule_type": "schedule",
  "scheduled_at": "2026-05-20T09:00:00Z",
  ...
}
Campaign queues at the scheduled time. You can cancel before then with DELETE /v1/sms/campaigns/:id.

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Tracking delivery

Get campaign status: 
curl https://api.nixflex.com/v1/sms/campaigns/smsc_a1b2c3d4 \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET"
Response includes per-recipient delivery status: 
{
  "campaign_id": "smsc_a1b2c3d4",
  "status": "completed",
  "recipients_count": 3,
  "sent_count": 3,
  "delivered_count": 3,
  "failed_count": 0,
  "replied_count": 1,
  "recipients": [
    {
      "phone_number": "+447111000001",
      "status": "delivered",
      "replied": true,
      "reply_text": "YES",
      "replied_at": "2026-05-17T03:48:12Z"
    }
  ]
}

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Handling replies

Replies are handled the same as one-off SMS: within the campaign’s reply window (default 24 hours), the agent automatically responds using context_prompt for context. Each reply triggers the agent to:
  1. Read the campaign’s context_prompt
  2. Read the agent’s system_prompt
  3. Read the original campaign message and the recipient’s reply
  4. Compose an appropriate response
If the reply triggers a booking, custom function, or other action, that runs too. The reply thread is logged as part of the campaign.

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List campaigns

curl https://api.nixflex.com/v1/sms/campaigns \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET"
Returns all campaigns for your account, newest first.

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Update or cancel

Before a campaign launches you can edit its body, recipients, or scheduled_at: 
curl -X PATCH https://api.nixflex.com/v1/sms/campaigns/smsc_a1b2c3d4 \
  -d '{"body": "Updated message text"}'
To cancel: 
curl -X DELETE https://api.nixflex.com/v1/sms/campaigns/smsc_a1b2c3d4
Cancelling a running campaign stops further sends; already-sent messages are not recalled.

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Rate limiting

Twilio rate-limits SMS at ~1 message per second per number by default. For larger campaigns, the engine paces sends accordingly. A 1,000-recipient campaign takes roughly 20 minutes to send fully. Need faster? Request a higher Twilio MPS limit from Twilio support, or add more sending numbers to your account.

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Compliance

Bulk SMS has stricter rules than one-off messages.
  • UK: Make sure all recipients opted in. Honour STOP keywords. Keep records.
  • US: Requires A2P 10DLC registration. Carriers will block unregistered traffic.
Sending without consent risks carrier blocking, fines, and your sending number being marked as spam.

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Costs

Same per-message Twilio billing as one-off SMS. No platform markup. Large campaigns can run into significant costs at scale — budget accordingly.