@Andy Donkel Thanks for reaching out. Can you please confirm which azure resource you have hosted your API and are you using APIM to expose those API's?
Assuming that you are hosting your API in azure webapps as per the tag added in the question and what to use APIM to access those API then to allow your third-party dev team to access your web app and API resources without giving them full access, you can create a new subscription in Azure API Management and configure it with the appropriate access policies. Here are the steps to create a new subscription.
Once you have created the subscription, you can configure it with the appropriate access policies to restrict access to your web app and API resources. For example, you can use IP filtering to restrict access to specific IP addresses, or you can use OAuth 2.0 to authenticate and authorize access to your APIs.
To configure OAuth 2.0 user authorization for the interactive test console in the Azure API Management developer portal, you can follow the steps outlined in the following document: Authorize test console of API Management developer portal using OAuth 2.0 user authorization.
Import webapps API to APIM you can refer to this document.