The Team API defines the way the team will operate with others. It provides the routine definitions, protocols, and tools used to engage with the team. Much like a software API, a consistent Team API makes it easier to build products, deliver value, and fix problems across the business.
At its basic level, the Team API should define:
The communication protocols between members of the team and anyone external to the team
The way the team accepts work items
The way the team delivers work items
The way the team shows progress on work items
When your engineering team consists of multiple teams, these points need to be consistent. It’s less important that the implementation is consistent, just that the Team API is.
Just as with the implementation of a software API, teams should be free to change their implementation of the Team API to focus on methods that work for them.
With this in mind, a good Team API should also:
Abstract away from how the team implements the API
Hide the internals of the team implementation of the API
Remain relatively stable
-- source: An API for Teams | Thoughts on Engineering
-- read more: Team Topologies by Matthew Skelton & Manuel Pais