Retrofit, don’t rebuild: Agentic overlays for transforming legacy enterprise services

2026-06-25 · Source: Artificial Intelligence · Field: Technology & Digital — Artificial Intelligence & Machine Learning, Software Development & Engineering, Cloud Computing & IT Infrastructure · Depth: Intermediate, long

Summary

Agentic overlays offer a pragmatic solution for integrating legacy REST-based enterprise services with emerging Agent-to-Agent (A2A) communication protocols. These thin wrapper layers transform traditional REST services into A2A-compatible agents without rewriting business logic or duplicating infrastructure. The solution addresses the challenge of bringing existing REST-based agents into a standardized A2A framework, which optimizes for reasoning-driven coordination and task-oriented messaging, unlike REST's deterministic client-server model. Reference architectures and sample Python code using Flask demonstrate an in-application overlay for message transformation from JSON-RPC 2.0 (A2A) to REST and back. The article also details using Amazon Bedrock AgentCore Gateway, Identity, Observability, and Runtime to decouple and manage agentic overlays at enterprise scale, supporting up to 10 targets per gateway and simplifying deployment and monitoring.

Key takeaway

For AI Architects evaluating how to integrate legacy REST services into emerging Agent-to-Agent (A2A) ecosystems, you should consider agentic overlays to avoid costly rebuilds. This approach allows your existing, stable business logic to participate in A2A communication by adding a thin translation layer. Implement within-application overlays for focused agents or use Amazon Bedrock AgentCore Gateway for scalable, decoupled enterprise deployments, reducing operational complexity and accelerating AI adoption without significant refactoring risk.

Key insights

Agentic overlays enable legacy REST services to participate in A2A communication without costly refactoring.

Principles

• A2A is a new interface, not a new API, for existing services.
• Preserve existing investments, extend where needed.
• Decouple agentic overlays for enterprise-scale flexibility.

Method

Implement a thin wrapper layer that transforms JSON-RPC 2.0 A2A messages to REST payloads and vice-versa, exposing REST endpoints as agent tools. This involves setting up agent cards, message endpoints, and translation logic.

In practice

• Use in-application overlays for single-service supervisor agents.
• Deploy AgentCore Gateway for multi-service orchestration.
• Implement A2A routes and message translation in Flask.

Topics

• Agent-to-Agent Communication
• REST APIs
• Agentic Overlays
• Amazon Bedrock AgentCore
• Enterprise AI Adoption
• Microservices Integration

Code references

• a2aproject/A2A

Best for: AI Engineer, MLOps Engineer, AI Architect

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Editorial summary, takeaway, and curation by AIssential. Original article published by Artificial Intelligence.