The agile team ...
Made up of 4 to 9 full-time people, including 1 to 3 technical experts who hold the technical vision and know how to translate it into implementation.
Is cross-functional. The team contains all of the skills necessary to design, build, and test the value to be delivered. Although it is possible for a team to divide this work up into roles, it is preferred that most members have or develop T-shaped skills to assist each other with bottlenecks.
Is self-organizing. Members are not assigned work by any one leader, but instead cooperatively and proactively select and share the work necessary to achieve their commitments.
Is self-managing. They hold each other accountable to their team commitments and working agreements.
Advocates for quality. It is expected that testing is baked in to every potentially shippable program increment (PSI) rather than relegated to an end stage.
Should be small and high performing. Any larger than nine people, and teams create silos and think in terms of “my” task and “your” task and not about getting the stories to “done”.