The Agent Protocols Stopped at the Client — Let's Talk About the Server Half

Description and use

Franca implements the missing server side of agent protocols, enabling secure, extensible tool execution and context handling while keeping clients lightweight.

Problem

Client‑side agent protocols lack a server‑side implementation, forcing developers to rely on vendor platforms, gateways, or raw inference endpoints, which limits agency, privacy, and extensibility.

Outcome

Franca restores the missing server side of agent protocols, enabling secure, extensible, and developer‑controlled tool execution while keeping clients lightweight.

Workflow

• 1. Add Franca dependencies to your Spring Boot project via Maven BOM and modules.
• 2. Configure adapters, drivers, and routes in application.yml to expose desired backends and tool types.
• 3. Implement server‑side tools as Spring beans implementing HostedToolHandler, returning JSON results.
• 4. Deploy the service; clients point their base_url to the Franca server and declare tool types only.
• 5. The server handles tool invocation, context propagation, and streams responses back to the client.
• 6. Extend or replace adapters/drivers as backends evolve without touching client code.

Evidence

Franca is my attempt at the missing piece: a Java 21 library that terminates both dialects inside your own service

Source

A server-side function is one bean: @Component public class HashToolHandler implements HostedToolHandler

Source

With that, your service is a standard OpenAI-compatible server. Clients point base_url at you and change nothing else.

Source