[Proposal] New experimental repository: experimental-cpb-slimrpc

[Tehsmash]

Abstract

This proposal requests the creation of an experimental-cpb-slimrpc repository under the a2aproject GitHub organization to host the SLIMRPC custom protocol binding for A2A.

SLIMRPC is an RPC protocol built on top of SLIM (Secure Low-Latency Interactive Messaging), an open-source network fabric developed by Agntcy. Rather than communicating over traditional HTTP URLs, agents connected to SLIM are addressed by a three-component hierarchical name (namespace/group/name), communicating through a SLIM node (broker/gateway). SLIM provides built-in identity management and a pub/sub messaging fabric, enabling agent-to-agent communication without the need for application-level authentication headers.

Motivation

The core A2A specification defines three standard bindings: HTTP+JSON, HTTP JSON-RPC, and gRPC. All three assume that agents are addressable via URLs and ports, which presupposes a conventional network topology.

SLIM represents a different networking model: agents are identified by structured names within a SLIM network rather than by host/port pairs, and authentication is established at the network layer by the SLIM runtime rather than via HTTP headers or TLS certificates managed by the application. This makes SLIM well-suited for scenarios such as:

• Edge and constrained environments where agents operate behind NAT or without stable IP addresses
• Multi-agent mesh deployments where agents need to discover and communicate with each other using a shared naming scheme rather than pre-configured URLs
• Simplified authentication where the SLIM network identity layer handles auth, removing the need for application-level credential management

These characteristics cannot be achieved by layering on top of the existing standard bindings, and warrant a dedicated custom protocol binding.

Specification

A draft specification for the SLIMRPC binding has been authored in the slimrpc_spec branch of Tehsmash/A2A. The binding reuses the same Protocol Buffer service definition (specification/a2a.proto) as the gRPC binding, and supports the full A2A method inventory including streaming via SLIM's unary-stream RPC pattern.

Reference Implementations

Two reference implementations are available with released support for A2A v0.3.0 and in-progress support for v1.0.0:

• Go: github.com/agntcy/slim-a2a-go
• Python: github.com/agntcy/slim-a2a-python

Request

Per the Extension and Protocol Binding Governance process, this proposal requests:

1. An A2A Maintainer to sponsor this proposal
2. Creation of the experimental-cpb-slimrpc repository under a2aproject

The initial content of the repository would be the existing spec draft and links to the reference implementations.

References

• SLIM project
• Agntcy organization
• SLIMRPC compiler documentation
• A2A Extension and Protocol Binding Governance
• A2A Custom Protocol Bindings

[msampathkumar]

Hi. I am new to A2A. Sharing my thought.

Q: So why not add this SLIMRPC to https://a2a-protocol.org/latest/community/#community-sdks - Community SDKs sections.

[Tehsmash]

Hi @msampathkumar Extensions and Custom protocol bindings need globally unique identifiers to enable interoperability between agents (i.e. if two agents state "stdio" as a protocol, you know they mean the same thing). A2A has https://github.com/a2aproject/A2A/blob/main/docs/topics/extension-and-binding-governance.md so that extensions and protocol bindings can be developed in the open, reserve a name in the a2a space, and potentially get promoted to an officially supported extension/binding.