Retrofit, don’t rebuild: Agentic overlays for transforming legacy enterprise services | Amazon Web Services

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Enterprise architectures have long been centered on REST APIs and microservices. These systems are stable, well-tested, and deeply embedded in production environments. They weren’t designed for Agent-to-Agent (A2A) communication, the emerging standard for autonomous agents that collaborate, reason, and coordinate through structured messaging. That worked in the absence of a common agent protocol, but it means many existing agents now sit outside the emerging A2A framework. The challenge today is no longer only adding A2A to traditional services. You also need to bring these REST-based agents into a standardized agent-to-agent world.

In this technical collaboration between AWS and the authors, we present a pragmatic solution: agentic overlays. Agentic overlays are thin wrapper layers that transform traditional REST-based services into agents capable of participating in A2A interactions. They also expose REST APIs as tools compatible...

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