Expose an Azure Function App via API Management@20aman Jan 07, 2020
You can expose an Azure Function App via API Management directly from within an Azure Function app. This functionality is provided out of the box and all you need to do is, configure the link between an Azure Function App and an existing (or new) API Management App.
To start, navigate to your Azure Function and click on the "Platform Features" tab. Here you will see the option for "API Management" as shown below.
Once you click on API Management, it takes you to a new blade. Here you can simply link your Function app to an existing API Management or even create a new one and then link the app.
Now that the app is linked, you can now manage API operations, apply policies, edit and download OpenAPI specification files, or navigate to API Management instance for a full-featured experience.
For more information please check this link: Create an OpenAPI definition for a serverless API using Azure API Management