In a nutshell: Agentic Overlays are thin wrapper layers that convert REST-APIs into A2A-capable agents without code duplication, eliminating the need for parallel infrastructures.
AWS and industry partners present an approach to integrate legacy systems without rewriting them into standardized agent-to-agent communication (A2A). Agentic Overlays enable existing REST-based services to act as autonomous agents and communicate via structured messaging.
Enterprise architectures are historically built on REST-APIs and microservices. These systems are stable, tested, and deeply embedded in production environments, but were not designed for agent-to-agent communication (A2A) — the new standard for autonomous agents that communicate in a structured manner, perform reasoning, and coordinate. This means that many existing agents today operate outside this new A2A framework and are run in parallel.
The technical problem: REST and A2A follow orthogonal paradigms. REST is optimized for deterministic client-server integration with predictable request-response flows and stable interfaces. A2A, by contrast, is optimized for reasoning-driven coordination between agents that discover each other, negotiate capabilities, and orchestrate multi-step tasks via JSON-RPC-based messaging. Agents can thereby plan actions, delegate tasks, and compose them across multiple services — not just call isolated endpoints.
The AWS solution relies on Agentic Overlays: thin wrapper layers that transparently transform traditional REST services into A2A agents. These overlays expose REST-APIs simultaneously as tools that conform to the Model Context Protocol (MCP). The central advantage: existing business logic remains unchanged, code is not duplicated, and no parallel infrastructure is created. This reduces agent sprawl through reuse of existing services.
The concept addresses a concrete migration problem: many agents deployed before A2A standardization are implemented as REST-based or proprietary services, with agent-specific logic directly in the endpoints. They now need to be integrated into standardized A2A protocols without rewriting their core logic. AWS provides reference architectures and sample code for this approach.
Source: aws.amazon.com · Published 25 June 2026
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