Retrofit, don’t rebuild: Agentic overlays for transforming legacy enterprise services
TL;DR
AWS presents agentic overlays as thin wrappers that make existing REST services participate in A2A workflows without rewriting business logic. The overlay translates agent messages into REST payloads and maps REST responses back into JSON-RPC-style A2A responses. REST endpoints can also be exposed as MCP-compatible tools, letting agents call existing enterprise capabilities. The post includes reference architectures and sample code, but it is visibly AWS and partner framed, so the positioning is PR-heavy.
Nauti's Take
The approach is pragmatic: existing services stay the source of truth, while agents get a new interface layer on top. That is often the right way to start enterprise AI.
But an overlay is not magic. If the underlying REST APIs are poorly documented, auth is inconsistent, or errors are messy, the agent layer only repackages those problems.
Strong migration pattern, weak excuse for postponing governance.
Briefingshow
Many enterprises already run stable REST services and do not want a second agent infrastructure next to the existing platform. The overlay idea matters because it treats migration as an interface problem, not a full rebuild. The hard part will be governance: auth, logging, failure modes, and tool permissions need to be as disciplined as the original service.
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