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

The authors propose a solution to transform legacy enterprise services into agents capable of participating in Agent-to-Agent (A2A) interactions using agentic overlays, a thin wrapper layer that exposes REST APIs as tools compatible with the Model Context Protocol (MCP). This approach allows enterprises to add A2A capabilities to existing REST services without rewriting business logic, duplicating code, or running parallel infrastructures. The agentic overlays enable autonomous agents to collaborate, reason, and coordinate through structured messaging, reducing agent sprawl in the infrastructure. The practical implication for engineers building AI systems is that they can leverage agentic overlays to integrate legacy services with A2A protocols, facilitating the adoption of AI in enterprise environments.

⚡ Key Takeaways

• Agentic overlays are a pragmatic solution to transform traditional REST-based services into agents capable of participating in A2A interactions.
• The Model Context Protocol (MCP) is used to expose REST APIs as tools compatible with A2A protocols.
• The approach reduces agent sprawl in the infrastructure by reusing existing services as agents.
• Reference architectures and sample code are provided to demonstrate how to build agentic overlays.
• The use of agentic overlays eliminates the need to rewrite business logic, duplicate code, or run parallel infrastructures.

The proposed solution enables enterprises to leverage their existing investments in legacy services while adopting A2A protocols, facilitating the integration of AI and autonomous agents into their systems. This approach can help reduce the operational complexity and cost associated with deploying and operating agentic infrastructures alongside existing enterprise systems.

✅ Practical Steps

1. Apply the concepts of agentic overlays to existing REST-based services to enable A2A interactions.
2. Use the Model Context Protocol (MCP) to expose REST APIs as tools compatible with A2A protocols.
3. Leverage reference architectures and sample code to build agentic overlays and integrate legacy services with A2A protocols.

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