You do not need every AI Agent to use the same framework.

The agents need to agree on the interface.
That is what protocols are for.

In http://Fetch.ai:

Agent A
Could be built with uAgents.

Agent B
Could contain completely different internal logic.

Agent C
Could connect through another framework or adapter.

They can still interoperate if they understand the same protocol.

A protocol defines things like:

→ What messages can be sent
→ What data those messages contain
→ Which responses are valid
→ How the interaction progresses

The Agent keeps its own internal logic. The protocol standardises the boundary.