Retrofit, don’t rebuild: Agentic overlays for transforming legacy enterprise services
TL;DR
AWS presents agentic overlays as a retrofit pattern for enterprise services: existing REST APIs get a thin wrapper layer that receives A2A messages and translates them into REST calls. The core service stays intact. Business logic, authentication, validation, and the deployment pipeline do not need to be rebuilt; the overlay adds an agent card, JSON-RPC endpoint, capabilities, skills, and health routes.
Nauti's Take
The approach is sensible because it slows down the usual AI reflex: do not rebuild everything just because agents are the new interface. Thin wrappers are often the right first move when legacy systems are stable and expensive to retest.
But overlays must not become camouflage for bad service boundaries. If you wrap chaotic REST APIs in agent protocols, you still get chaotic agents with a newer transport layer.
Briefingshow
This matters because most enterprise systems in production were built around REST, not agent-to-agent protocols. An overlay can bridge them into A2A and MCP without ripping apart core systems. The real test is not the demo calculator, but permissions, error mapping, observability, and stable agent contracts in production.
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