Enterprises relying on legacy REST-based microservices face difficulties adopting agentic architectures that require agent-to-agent (A2A) communication. Traditional REST services, designed for deterministic client-server interactions, do not naturally support the structured messaging and multi-step reasoning protocols used by autonomous agents. To bridge this gap without rebuilding or duplicating existing infrastructure, AWS recently proposed using agentic overlays, which act as thin wrapper layers that convert legacy services into participants in the A2A ecosystem.

Agentic overlays function by transforming A2A-compliant JSON-RPC 2.0 messages into standard REST payloads and vice versa. This approach exposes legacy REST endpoints as tools or agent skills, allowing enterprises to integrate A2A capabilities without altering underlying business logic or creating parallel deployment pipelines. By using a single deployment process for both REST and A2A interfaces, organizations can reduce infrastructure complexity and mitigate the challenges associated with managing separate agentic and non-agentic environments.

As a practical demonstration of this design pattern, a legacy calculator service built with Flask can be adapted for A2A interoperability. The implementation process involves creating a dynamic agent card that provides metadata for agent discovery and implementing a translation layer. This layer handles JSON-RPC 2.0 requests by mapping specific tasks to corresponding REST endpoints, forwarding authentication headers, and translating REST responses back into the A2A message format. The provided architecture is particularly effective for supervisor agents that require both standard REST execution and agentic coordination, such as intent classification and automated request routing.

Enterprises relying on legacy REST-based microservices face difficulties adopting agentic architectures that require agent-to-agent (A2A) communication. Traditional REST services, designed for deterministic client-server interactions, do not naturally support the structured messaging and multi-step reasoning protocols used by autonomous agents. To bridge this gap without rebuilding or duplicating existing infrastructure, AWS recently proposed using agentic overlays, which act as thin wrapper layers that convert legacy services into participants in the A2A ecosystem.

Agentic overlays function by transforming A2A-compliant JSON-RPC 2.0 messages into standard REST payloads and vice versa. This approach exposes legacy REST endpoints as tools or agent skills, allowing enterprises to integrate A2A capabilities without altering underlying business logic or creating parallel deployment pipelines. By using a single deployment process for both REST and A2A interfaces, organizations can reduce infrastructure complexity and mitigate the challenges associated with managing separate agentic and non-agentic environments.

As a practical demonstration of this design pattern, a legacy calculator service built with Flask can be adapted for A2A interoperability. The implementation process involves creating a dynamic agent card that provides metadata for agent discovery and implementing a translation layer. This layer handles JSON-RPC 2.0 requests by mapping specific tasks to corresponding REST endpoints, forwarding authentication headers, and translating REST responses back into the A2A message format. The provided architecture is particularly effective for supervisor agents that require both standard REST execution and agentic coordination, such as intent classification and automated request routing.