Authenticated Calls with Microsoft Teams
Prerequisites
An active Azure subscription is required. Registering the Azure Communication Services (ACS) service principal in your tenant only works if the tenant has an active Azure subscription linked. If you don't have one, create/activate a subscription in the Azure portal before proceeding. Otherwise the service principal creation will fail.
If your tenant doesn't have one, follow the official Microsoft guide to create it: https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/create-subscription
You will also need:
Global Administrator (or Privileged Role Administrator) rights on the Microsoft 365 tenant
Your Tenant ID (Entra ID → Overview)
PowerShell 5.1 or PowerShell 7+
Requirements
To enable authenticated calls with Microsoft Teams, the following prerequisites must be met.
Azure Communication Services service principal
Microsoft Teams interoperability for third party applications relies on Azure Communication Services (ACS).
To allow authenticated calls, the Microsoft tenant must contain the Azure Communication Services service principal. This component allows applications to authenticate Teams identities and join meetings through the Microsoft communication APIs.
🔍︎ Check if the Azure Communication Services service principal is installed
An administrator can verify whether the ACS service principal already exists in the tenant.
Sign in to the Azure portal
Go to Microsoft Entra ID > Enterprise Applications > All Applications

Clear any filters that may be applied

In the search field, search for "Azure Communication Services"

If the application appears in the list, the ACS service principal is already installed and no further action is required.
If the application does not appear in the list, follow the next steps to proceed with the installation.
✅ Installing the Azure Communication Services service principal
If the ACS service principal is not present in the tenant, it must be created by an administrator.
Step 1. Open PowerShell
Open the Azure Portal and start a PowerShell session with administrative privileges.

Step 2. Install the Microsoft Graph module (if not already installed)
Install-Module Microsoft.Graph -Scope CurrentUserStep 3. Connect to your tenant
Replace TENANT_ID with your tenant ID. Find your tenant ID here.
Connect-MgGraph -TenantId "TENANT_ID" -Scopes "Application.ReadWrite.All"A Microsoft authentication URL or window will appear where the administrator must sign in.
Step 4. Create the Azure Communication Services service principal
Run the following command:
New-AzureADServicePrincipal -AppId "1fd5118e-2576-4263-8130-9503064c837a"This registers the Azure Communication Services service principal in the tenant and enables authenticated Teams calls for supported applications.
(Optional) Using Azure CLI instead
If you prefer not to install PowerShell modules, you can achieve the same with the Azure CLI:
az login --tenant TENANT_ID
az ad sp create --id 1fd5118e-2576-4263-8130-9503064c837aSetup scenarios

When authentication is not configured
If authentication is not enabled, Mago can still join meetings as a guest participant.
In this scenario:
• the system may enter the meeting lobby • the participant appears as a generic device name • some meeting features may behave differently depending on the host organization’s policies

