If you need to develop a connector that has your data from your internal application, or to a
third-party service that does not exist yet on the connectors, you can use the internal Webhook connector that is built in to Microsoft Teams to create your own connection to a channel using standard protocols, such as HTTP, to pull your data from the source of your application:

1. To use the Incoming Webhook, add a connector, select it, and click on the Add button. The following screenshot shows the connector of the incoming Webhook:

2. To create a Webhook, specify a name, update the image of the Webhook if necessary, and click on the Create button. The following screenshot shows the incoming Webhook configuration:

3. To learn more about Office 365 connectors, go to https://docs.microsoft.com/en-us/outlook/actionable-messages/card-reference. You can also create cards, using the example at https://docs.microsoft.com/en-us/outlook/actionable-messages/actionable-messages-via-connectors.

If your team needs to create custom connectors and a connection to your internal or external applications, follow the guide at https://msdn.microsoft.com/en-us/microsoft-teams/connectors.