Configure outgoing SMS in ElevenLabs
Connect an ElevenLabs webhook tool to your Atom SMS service to send outgoing messages.
This guide covers tool setup and testing only. It does not configure incoming SMS or two-way replies.
Before you begin
Make sure you have:
- Access to create and manage an SMS service in the Atomic portal.
- Access to create webhook tools and secrets in ElevenLabs.
- A sender number or Sender ID authorised for your Atom SMS service.
- A mobile number you control for the test.
Keep your API key secure: Do not include it in screenshots, support tickets or chat messages. If a key is exposed, revoke it and generate a replacement.
Create the SMS service
Navigate: Services > SMS
Step 1: Sign in to the Atomic portal.
Step 2: In the sidebar, open Services then select SMS.
Step 3: Select Add Service.
Step 4: Complete the required service details and save the service.
Generate the API key
Step 1: Return to the SMS service list, find the service you created then select Manage.
Step 2: In the SMS service, open API Keys and select Generate API Key.
Step 3: When the Success! message appears, select Close. A new row appears under API Keys with the name field empty.
Step 4: To add an optional name, select the pencil icon in the new row, enter a name such as
ElevenLabs in the Add key name... field then select the save icon.Step 5: Select Show in the new row, copy the API key and store it securely. You will use it when creating the ElevenLabs secret.
Enable Automation
Step 1: Scroll to Manage Service at the bottom of the SMS Service Configuration.
Step 2: Set Automation to On and leave Block Service set to Off.
Step 3: Save the service if prompted.
Step 4: Refresh the page and confirm that Automation is On and Block Service is Off.
Create the webhook tool
Navigate: ElevenAgents > Tools > Webhook Tools
Step 1: Sign in to ElevenLabs.
Step 2: Open ElevenAgents using the option that applies to you:
- First sign-in: On the Choose your platform page, select ElevenAgents then select Continue.
- Returning user: ElevenLabs opens the platform you previously selected. If you are already in ElevenAgents, continue to Step 3. Otherwise, use the product switcher at the bottom left to select ElevenAgents.
Step 3: Open Tools then select Add Webhook Tools.
Step 4: Create a new webhook tool.
Configure the webhook
Step 1: Return to the SMS service you created in Atomic.
Step 2: Under Service Details, copy the SMS API URL then add
/sms/send to the existing /api path.Example:
https://sms.example.com/api/sms/sendStep 3: Return to the ElevenLabs webhook tool and enter these settings:
4 of 4 rows
| Name | Atomic_SMS |
| Description | Sends an SMS through the configured Atom SMS service. |
| Method | POST |
| URL | Your SMS API domain followed by /api/sms/send |
The URL should follow this structure:
text
https://<your SMS API domain>/api/sms/send
Use your service's URL: Use the domain shown in your own SMS service. Do not copy a domain from an example or add /api/sms/send twice.Add the Authorization secret
Step 1: In Headers, select Add header and enter:
2 of 2 rows
| Type | Secret |
| Name | Authorization |
Step 2: Under Secret, select Add new secret.
Step 3: Enter a clear name such as
Atomic_SMS_API_Key.Step 4: In Value, paste the API key generated from the Atom SMS service's API Keys section.
Step 5: Save the secret.
Step 6: Select the new secret for the
Authorization header.Use a secret: Keep the API key in the ElevenLabs secret. Do not put it in the tool description, agent prompt or body parameters.
Add the body parameters
Step 1: In Body parameters, select JSON and enter a Description such as: Send an SMS using the configured sender, recipient number and message text.
Step 2: Under Properties, select Add property.
Step 3: Set Data type to String, enter the parameter name in Identifier and select Required.
Step 4: Choose a Value Type and complete the corresponding value, variable or Description. Use the example below as a guide and choose the value types that suit your use case:
3 of 3 rows
from | Constant Value | Enter the sender number or Sender ID authorised for this Atom SMS service. Use only the configured sender. |
to | Dynamic Variable | Select a variable containing the intended SMS recipient's mobile number in the international format accepted by the Atom SMS service. |
text | LLM Prompt | The plain-text SMS message requested or approved by the user. |
Step 5: Select Add property again and repeat Steps 3 and 4 for the remaining parameters until
from, to and text are all listed.Step 6: For
to, verify that the selected variable contains the intended SMS recipient's number. To collect the number during the conversation instead, use LLM Prompt and describe how to obtain it.Use the configured sender: Do not let the agent choose or invent a sender. Keep the API key separate from these message parameters.
Save and test the tool
Step 1: Select Add tool to save the webhook tool then open Test tool.
Step 2: Confirm that
from uses the authorised sender configured on the Atom SMS service.Step 3: Make sure
to resolves to a mobile number you control, including when it uses a dynamic variable.Step 4: Enter a short test message in
text and run the test.Step 5: Confirm that the tool reports a successful response.
Step 6: Check that the SMS arrives at the destination number.
The test is complete when the tool receives a successful response and the SMS arrives. A successful API response alone does not confirm delivery to the phone.