Send text messages from your agents using Twilio, Plivo, Vonage, Sinch, Telnyx, or Msg91.

SMS Tool

Let your agents send text messages to users, customers, or leads. The SMS tool supports multiple providers, works with both chat and voice agents, and is perfect for confirmations, reminders, and follow-ups.

Supported SMS Providers

thinnestAI supports six major SMS providers. Choose the one that fits your region, pricing, and existing infrastructure:

Provider	Best For	Regions
Twilio	Most popular, widest coverage. Great default choice.	Global
Plivo	Cost-effective alternative to Twilio with strong API.	Global
Vonage (Nexmo)	Enterprise-grade messaging with excellent European coverage.	Global
Sinch	Strong in Europe and Asia. Good for high-volume messaging.	Global
Telnyx	Developer-friendly with competitive pricing.	Global
Msg91	Specialized in India. Best deliverability for Indian numbers.	India-focused

Setting Up the SMS Tool

Step 1: Get Provider Credentials

Twilio:

TWILIO_ACCOUNT_SID=ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
TWILIO_AUTH_TOKEN=your_auth_token
TWILIO_PHONE_NUMBER=+15551234567

Plivo:

PLIVO_AUTH_ID=your_auth_id
PLIVO_AUTH_TOKEN=your_auth_token
PLIVO_PHONE_NUMBER=+15551234567

Vonage:

VONAGE_API_KEY=your_api_key
VONAGE_API_SECRET=your_api_secret
VONAGE_PHONE_NUMBER=+15551234567

Sinch:

SINCH_KEY_ID=your_key_id
SINCH_KEY_SECRET=your_key_secret
SINCH_PHONE_NUMBER=+15551234567

Telnyx:

TELNYX_API_KEY=your_api_key
TELNYX_PHONE_NUMBER=+15551234567

Msg91:

MSG91_AUTH_KEY=your_auth_key
MSG91_SENDER_ID=your_sender_id

Step 2: Configure the SMS Tool

Navigate to Agents and select your agent.
Go to the Tools section and click Add Tool.
Select SMS.
Choose your SMS provider from the dropdown.
Enter your provider credentials.
Set the From Number — the phone number messages will be sent from.
Save.

Step 3: Assign to an Agent

In your agent's instructions, tell it when and how to use SMS:

You can send text messages to users. Use SMS for:
- Appointment confirmations
- Sending links or codes that are easier to reference as text
- Follow-up information after a call

Always ask for permission before sending a text.
Keep messages concise (under 160 characters when possible).

Sending SMS from an Agent

Chat Agent Example

User:   "Can you text me the meeting link?"
Agent:  "Sure! What's your phone number?"
User:   "555-0198"
Agent:  [Sends SMS to +15550198: "Here's your meeting link:
         https://meet.thinnest.ai/abc123 — See you at 3 PM!"]
        "I've sent the meeting link to your phone. You should
         receive it in a moment."

Voice Agent Example

During a voice call, the agent can send an SMS while continuing the conversation:

Agent:  "I found three properties that match your criteria. Would you
         like me to text you the listings so you can review them?"
Caller: "Yes, please."
Agent:  [Sends SMS with property links while continuing the call]
        "Great, I've just sent you a text with links to all three
         properties. Let me walk you through the highlights of each one..."

SMS Mid-Call Actions

One of the most powerful features is sending SMS messages during a live voice call. This allows your voice agent to:

Send links — Share URLs that are hard to communicate verbally.
Send confirmation details — Booking confirmations, order numbers, reference codes.
Send documents — Links to PDFs, contracts, or forms.
Send follow-up info — After-call summaries while the conversation is still fresh.

Configuring Mid-Call SMS

Open your voice agent configuration.
In the Tools section, ensure SMS is added and configured.
In the agent instructions, describe when to send texts during calls:

During phone calls, use SMS to:
- Send booking confirmation after scheduling an appointment
- Share links to forms or documents the caller needs
- Send a summary of the call at the end

When sending an SMS during a call:
1. Ask the caller if they'd like a text
2. Confirm their phone number (you may already have it from caller ID)
3. Send the text
4. Let them know it's been sent

Example: Appointment Reminder with SMS Confirmation

Build a voice agent that books appointments and sends SMS confirmations.

Agent Setup

Field	Value
Name	Booking Agent
Model	GPT-4o
Tools	Google Calendar, SMS

Agent Instructions

You are a booking assistant for Acme Wellness Center.

BOOKING FLOW:
1. Greet the caller and ask what service they'd like
   (massage, facial, consultation)
2. Ask for their preferred date and time
3. Check Google Calendar availability
4. If available, book the appointment
5. Ask: "Would you like me to text you a confirmation?"
6. If yes, send an SMS with:
   - Service type
   - Date and time
   - Address: 123 Wellness Ave, Suite 200
   - Cancellation policy: 24 hours notice required

SMS FORMAT:
"Confirmed: [Service] at Acme Wellness Center
Date: [Day], [Date] at [Time]
Location: 123 Wellness Ave, Suite 200
To reschedule, call (555) 012-3456.
24hr cancellation policy applies."

Sample Call

Agent:   "Hello! Thank you for calling Acme Wellness Center. How can
          I help you today?"

Caller:  "I'd like to book a massage for this Saturday."

Agent:   "I'd love to help with that. What time works best for you?"

Caller:  "Around 2 PM?"

Agent:   [Checks Google Calendar — 2 PM Saturday is available]
         "Saturday at 2 PM is available! Your massage is booked.
          Would you like me to send you a text confirmation?"

Caller:  "Yes, please."

Agent:   [Sends SMS: "Confirmed: Massage at Acme Wellness Center
          Date: Saturday, March 8 at 2:00 PM
          Location: 123 Wellness Ave, Suite 200
          To reschedule, call (555) 012-3456.
          24hr cancellation policy applies."]
         "Done! I've sent the confirmation to your phone. Is there
          anything else I can help with?"

SMS Best Practices

Message Content

Keep messages under 160 characters when possible to avoid splitting.
Include the business name so recipients know who it's from.
Add a way to opt out or contact you for important/recurring messages.

Compliance

Always get consent before sending SMS. Your agent should ask permission.
Follow local regulations (TCPA in the US, GDPR in Europe).
Include opt-out instructions for marketing messages.
Don't send SMS outside business hours unless it's time-sensitive.

Deliverability

Use a verified phone number with your provider.
Register your number for A2P (Application-to-Person) messaging if required.
Monitor delivery rates in your provider dashboard.

Troubleshooting

Issue	Solution
SMS not delivered	Check provider dashboard for delivery status. Verify the recipient number format includes country code (+1 for US).
"Invalid credentials"	Double-check your provider API key/token. Ensure the account is active.
Messages split into multiple texts	Keep messages under 160 characters or accept multi-part SMS (most providers handle this automatically).
"From" number not working	Verify the number is SMS-enabled in your provider's dashboard. Some numbers are voice-only.

Next Steps

Google Calendar — Pair SMS with calendar for full booking automation.
CRM & Webhooks — Log SMS interactions in your CRM.
Custom Tools — Build custom integrations for advanced messaging workflows.

SMS Tool

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