All of this protocol crap is a distraction. What's important is allowing agents talk to each other in their current scope and ACLs, including for their ability to talk to and discover tools. When Anthropic decided MCP was a good idea and published what they did, I ranted for days. Ok, I'm still ranting.

Now, discovery is important and there is a post right now on the front page about it. But what everyone is probably missing is that a) agents with tokens and services that honor those tokens is already handled well with HTTP. Fun fact, the original HTTP protocol (does anyone do RFCs anymore?) didn't support POSTs! So, most calls can be boiled down to doing a GET request somewhere with a token the remote end understands. Layer on SSL to hide the ? parameters, assuming it's easy to get certs mapped to your house network.

Discovery can be handled a bunch of different ways but given the nature of where the agents are running, it can be DIFFICULT to connect them (hole poking comes to mind). Of course you could run stuff in the cloud. But, if you care about sovereignty, you probably want to avoid anything that will "lock" you into a service (or a single agent/model for that matter).

What's 100% missing is payments, of course. Meet the 402, PAYMENT REQUIRED. Cloudflare (grumble) has something for that, but they stole it from Lightning Lab's very own roasbeef's Aperture project a while back, which implements payments with the Lightning network.

Make a bulk payment to a Bitcoin address. Stuff it in a Lightning invoice, send it to someone, they extract it and update the server to let you in. If you decided they ripped you off, close the invoice and the funds are refunded.

Now, I know a lot of people are skeptical about Bitcoin, but I really do think micropayments are useful for agent-to-agent comms. That's why I threw down the idea on a page about two years ago...so I wouldn't' forget: https://ahp.nuts.services/

AI infrastructure/tools developer here (www.hic-ai.com). I considered the A2A protocol carefully, but I decided a while ago that, from my perspective, the A2A protocol was not solving the correct problem. There is no distinction (from the perspective of an agent) between a communication from Agent A to Agent B, on the one hand, and a communication from Agent A to "future Agent A", on the other. In fact, agents have no inherent sense of identity at all, so there is no inherent notion of a unique Agent A. The notions like "Agent A" received a message or that "Agent A" is sending a message to a different agent (or to its future self) are all inextricably intertwined with the idea of an agentic identity existing and being well defined in the first place, which it is not. The A2A protocol assumes the existence of such a well-defined agent identity in its presumption that agent cards point to a specific agent that can be discovered and deployed. I also think gRPC adds a significant layer of indirection and obfuscation, plus it's painful to implement. The lack of widespread adoption suggests that A2A is not really solving a real-world problem, compared to MCP, for instance.

Not to great effect, AFAIK. Laurie Voss (creator of npm) had a good presentation a few months back on all the different agent interaction protocols, and was skeptical whether they (including A2A) added much value. https://youtu.be/kqB_xML1SfA?si=lxehX1-_z_dBoZtQ

If you're big in the google ecosystem it makes sense:

- gemini-cli can have remote a2a agents connected to it. (See https://github.com/tanaikech/gemini-cli-gas-a2a-subagents and the medium article linked in that repo description.) Haven't tried it but I tried the local use case below.

- can expose a custom Google ADK "agent" via one-liner as a2a, which you can connect to the gemini-cli the same way.

I am using A2A at work. It's a bit like the "microservices architecture" for agents... Allows you or teams to develop agents independently and have them interact as and when they need to. No major hurdles so far.

A2A solves the problem of independently developed agents talking to each other. The bigger problem is "how do i trust your agent works?", which would be solved by having a believable system of Agent Evals, so I could test that your Agent actually does what it says on the box. Otherwise an Agent Directory and automatic dispatch of agents is close to useless.

Related. Others?

The Agent2Agent Protocol (A2A) - https://news.ycombinator.com/item?id=43631381 - April 2025 (280 comments)

Seems like over engineering just build an API in front of your agent, give the other agent the spec in a markdown file.

On the vscode team we're rebuilding our agent infrastructure on top of a new protocol, AHP: https://github.com/microsoft/agent-host-protocol.

It's a common protocol for talking to a host of multiple agents/harnesses.

Ya, we tried it a bit, but have stayed with agent-behind-MCP style patterns for now. I think A2A or something like it will become a big thing as everything matures. It just felt over complicated for our use case. One misconception I had was we would just slap A2A on our existing agents and they’d work well together. Kind of dumb in hindsight.

(Based off 2-3 month-old recollection, take with a grain of salt)

I had wanted to use it for my agent "network". A2A didn't fit the use case of "trusted agent, and was bloated due to "what if rogue actor". Of course, I could have used it, with all of its roughness, but chose to just vibe my own (before Claude Teams, though I haven't really used that, I think). In the process of creating a server to handle this (I already set up a Scala webserver to administrate/orchestrate hooks). Would love to hear others' suggestions for this.

I know our sales/business team is pitching it quite a bit (instead of our current end-to-end solution we provide), but no one has quite been able to define the boundaries of how that interacts when we don't own the full solution. Curious how others have been using it. Definitely seems designed for more of an internal or B2B use case where agents have super well defined behavior but are ultimately behind some other system entirely.

I'm using it at work as well. It's quite challenging to manage.

I've changed my mind a few times on this, but given how substantial the adoption for MCP has been (Claude and OpenAI both use it for their native integrations) its only a matter of time before consolidation happens.

There's a way higher incentive to build an MCP server than an A2A one, and unless Google makes their default AI search a native A2A client it doesn't feel like it will get the momentum it needs to take off.

In the past 1 year, I think I've moved from MCP to A2A to Agent <> MCP back again. I have agents still talking to other Agents via A2A for some use cases, but for the most part, it's back to Agent <> MCP now; couple that with tool search/code mode (whatever you want to call it) in your Agentic AI harness, MCPs seem to be the way to go for now.

We set up something with a registry of AgentCards and a messaging system with SSE streaming—then we realized we didn’t need an agent on the other side so now we have this weird hybrid pattern.

So, no.

I work at some megacorp and have direct insight about any ai use - nope, not a single use case i witnessed used a2a in the final product. I still don't get a2a but you probably have to work at Google or something to see this as the solution to something.

Yes. My agent speaks A2A with itself and others. But my agent is built in layers like an organization.

No. I have seen ACP be incredibly helpful in the IDE sense and in things like zo.computer

No, it was designed on paper by someone with no understanding of prompt caching and no consideration of latency or token costs

I had the same question in mind while reading another submission on the front page: https://news.ycombinator.com/item?id=48573268

I am not using A2A. I think it is too early for such a thing.

I uh…still use tmux send-keys. I’ll change as soon as I find a use-case it doesn’t solve. ¯\_(ツ)_/¯

enterprises are, its the future for them. Take a look: https://www.tigera.io/blog/why-we-built-lynx-bringing-contro...