Docs - AI phone agents for SMB

An agent’s functions are stored as entries in extensions.tools. To add an SMS function through the API, add the entry below to extensions.tools on Create Agent or Update Agent. These are the same entries the Telzino Dashboard writes when you add the function under Functions.

extensions is replaced whole. Read the agent with Get Agent, add your entry to the existing extensions.tools array, and send the whole extensions object back. If you send only the new entry, every other function on the agent is removed.

Which function to use

You want to	Use	Tool `type`
Send texts through the organization’s Twilio connection	Send SMS via Twilio	`twilio_sms`
Send texts from a Telzino hosted SMS number	Send SMS via hosted SMS	`hosted_sms`
Send texts through NetSapiens	Send SMS via NetSapiens	`netsapiens`
Keep an existing Notify (call summary) function	Notify	`notification`

The agent decides when to text, who to text and what to say from the instructions you give it in the function. See Send SMS for writing them.

Rules for every entry

The API validates each entry in extensions.tools against a strict schema. A key it doesn’t recognise is rejected with 400.

Field	Type	Notes
`name`	string	The function’s name. Use the exact names below.
`type`	string	One of the allowed tool types, for example `twilio_sms`, `hosted_sms`, `netsapiens` or `notification`.
`friendlyName`	string	Display name.
`description`	string	What the function does. The dashboard sets it to the same text as the instructions.
`condition`	string	When the function can run. SMS functions use `during_call`.
`url`	string	Must be a valid URL. SMS functions use an `internal://` address, shown below.
`method`	string	`GET`, `POST`, `PUT`, `PATCH` or `DELETE`. The dashboard writes `POST`.
`headers`	array	`{ "key", "value" }` pairs. The dashboard writes `Content-Type: application/json`.
`parameters`	array	`{ "key", "value" }` pairs, where `value` is a string.
`enabled`	boolean	Optional. Not used by SMS functions.

The schema marks every field as optional, but send the full entry as shown so the agent and both editors read it the same way.

Send SMS via Twilio

The agent texts through the organization’s Twilio connection. Set up the connection first in the Telzino Dashboard or the Connect App.

{
  "name": "send_sms_via_twilio",
  "type": "twilio_sms",
  "friendlyName": "Send_SMS",
  "condition": "during_call",
  "url": "internal://twilio-sms-service",
  "method": "POST",
  "headers": [{ "key": "Content-Type", "value": "application/json" }],
  "description": "If the caller requests a confirmation, send them an SMS with the appointment details.",
  "parameters": [
    { "key": "sms_instructions", "value": "If the caller requests a confirmation, send them an SMS with the appointment details." },
    { "key": "from_number", "value": "+15555550100" }
  ]
}

Parameter	Required	Value
`sms_instructions`	Yes	When and what to text. The dashboard uses the text shown above when this is left blank.
`from_number`	See note	The number this agent texts from, in E.164 format.

From number: a new or changed Send SMS entry needs a From number, either in from_number or in the agent’s integrations.twilio.fromNumber. If neither has one, the request is rejected with 400 and the message Send SMS needs a From number. Add one to the function, or remove the function. An entry that is already stored without a number is not re-checked when you send it back unchanged.
Twilio credentials can’t be set on an agent. Every agent in the organization uses the organization’s Twilio connection. See integrations on Update Agent.
Writing integrations.twilio through the API does not add this entry. Add it yourself.

Send SMS via hosted SMS

The agent texts from one of the organization’s hosted SMS numbers. Hosted SMS is set up by Telzino on request. See Send SMS.

{
  "name": "send_hosted_sms",
  "type": "hosted_sms",
  "friendlyName": "Send_Hosted_SMS",
  "condition": "during_call",
  "url": "internal://hosted-sms-service",
  "method": "POST",
  "headers": [{ "key": "Content-Type", "value": "application/json" }],
  "description": "If the caller requests a confirmation, send them an SMS with the appointment details.",
  "parameters": [
    { "key": "sms_instructions", "value": "If the caller requests a confirmation, send them an SMS with the appointment details." },
    { "key": "from_number", "value": "+15555550100" }
  ]
}

from_number must be one of the organization’s hosted SMS numbers. A new or changed number is checked when you save, and an unowned number is rejected with 400.
If Hosted SMS is locked for the organization in Feature Administration, a request that adds this entry is refused with 403. Sending back, editing or removing an existing entry is still allowed.

To let the agent read the caller’s replies, also add check_hosted_sms_replies:

{
  "name": "check_hosted_sms_replies",
  "type": "hosted_sms_replies",
  "friendlyName": "Check_Hosted_SMS_Replies",
  "condition": "during_call",
  "url": "internal://hosted-sms-service",
  "method": "POST",
  "headers": [{ "key": "Content-Type", "value": "application/json" }],
  "description": "When to check whether the caller has texted back.",
  "parameters": []
}

Send SMS via NetSapiens

The agent texts through NetSapiens, using the agent’s own SMS number as the sender. The agent needs the NetSapiens integration. See Send SMS (Voip UCAAS).

{
  "name": "ns_send_sms",
  "type": "netsapiens",
  "friendlyName": "Send_Sms",
  "condition": "during_call",
  "url": "internal://netsapiens-service",
  "method": "POST",
  "headers": [{ "key": "Content-Type", "value": "application/json" }],
  "description": "Text the caller the office address when they ask for directions.",
  "parameters": [
    { "key": "instructions", "value": "Text the caller the office address when they ask for directions." }
  ]
}

To read replies, add a second entry with the same shape, "name": "ns_check_sms_replies" and "friendlyName": "Check_Sms_Replies".
If SMS Messaging is locked for the organization in Feature Administration, a request that adds ns_send_sms or ns_check_sms_replies is refused with 403. Sending back or removing an existing entry is still allowed.

Notify

The Notify function sends a call summary at the end of the call. The Telzino Dashboard no longer offers Notify under Add function, but agents that already have it keep it, and the API still accepts the entry:

{
  "name": "Notify_Email",
  "type": "notification",
  "friendlyName": "Send_Email_Notification",
  "condition": "end_of_call",
  "url": "https://your-email-service.com/api/send-notification",
  "method": "POST",
  "headers": [{ "key": "Content-Type", "value": "application/json" }],
  "description": "Send a summary to [email protected] and text +15555550100 after every call.",
  "parameters": [
    { "key": "notification", "value": "Send a summary to [email protected] and text +15555550100 after every call." }
  ]
}

The recipients and conditions are written in plain language in the notification parameter, as described on Notify. The dashboard stores the url above as a placeholder.
Don’t give a Notify entry a name starting with ns_chat or NS_Chat, or a notification value containing "type": "ns_chat": those mark it as a NetSapiens Chat Notification instead.

To email a summary after every call, you don’t need a function: set email (and optionally sendRecordingLinkWithSummary) on Update Agent.

Example: add Send SMS via Twilio

Read the agent:

curl https://api.telzino.com/v1/agents/AGENT_ID \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN"

Copy extensions from the response, add the Send SMS entry to extensions.tools, and send it back:

curl -X PUT https://api.telzino.com/v1/agents/AGENT_ID \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "extensions": {
      "tools": [
        { "...": "the agent'\''s existing tools, unchanged" },
        {
          "name": "send_sms_via_twilio",
          "type": "twilio_sms",
          "friendlyName": "Send_SMS",
          "condition": "during_call",
          "url": "internal://twilio-sms-service",
          "method": "POST",
          "headers": [{ "key": "Content-Type", "value": "application/json" }],
          "description": "When a caller books an appointment, text them the date, time and address.",
          "parameters": [
            { "key": "sms_instructions", "value": "When a caller books an appointment, text them the date, time and address." },
            { "key": "from_number", "value": "+15555550100" }
          ]
        }
      ]
    }
  }'

Replace the placeholder line with the agent’s real existing entries, and keep the other keys from extensions. MCP connections come back from Get Agent in their stored shape, so convert them to the request shape before sending them back. See Get Agent: Stored MCP Connection Shape.

Read the agent again to confirm the entry was saved. The change appears in Change History.

API Reference

Agents

SMS Templates

Places

MCP

Knowledge Bases

Guardrails

Email Servers

Email Templates

Voices

Custom Voices

STT Providers

LLM Models

Features

Call Logs

Outbound Calls

Retry Policies

Suppression List

Metrics

Reports

Resellers

Organizations

Sessions

Chat

Billing

Payments

Event Webhooks

SMS Functions in extensions.tools

Which function to use

Rules for every entry

Send SMS via Twilio

Send SMS via hosted SMS

Send SMS via NetSapiens

Notify

Example: add Send SMS via Twilio