OGP, A2A, and MCP

OGP, A2A, and MCP: Three Lanes, Same Highway

The Confusion Is Fair
I spent an embarrassing amount of time recently explaining why OGP wasn't "just MCP for agents" or "A2A with extra steps."
The confusion is fair. All three involve agents talking to something beyond their immediate prompt window. All three matter. And all three can show up in the same stack.
But they live at different layers.
If you blur those layers together, you don't get elegant interoperability. You get architectural mush: the wrong protocol solving the wrong problem, until six months later you're debugging why messages are disappearing between systems that are supposedly "connected."
The cleanest way I know to say it is this:
MCP
is the tool layer
A2A
is the agent interoperability layer
OGP
is the trust-and-coordination layer across gateways
Same highway. Different lanes.
Start With The Real Problem
The real problem OGP is trying to solve is not "how can one agent call a tool?" and not even "how can multiple agents cooperate in principle?"
It's this:
How do agents that live in different operational domains coordinate safely, explicitly, and predictably?
That means crossing boundaries like:
personal vs work
laptop vs VPS
home network vs public internet
one admin domain vs another
one human's agent vs another human's agent
That is a different problem from tool access. It is also a different problem from generic agent task delegation.
It is the problem of federation with trust.
That is OGP's lane.
MCP: The Tool Belt
Model Context Protocol is about exposing capabilities to an agent in a structured way.
That's why MCP has taken off. It solves a real and ugly problem: if an agent needs access to files, browsers, databases, APIs, or prompts, how do you present those capabilities in a way the agent can discover and use reliably?
MCP is great for:
exposing tools to an agent
exposing resources and prompts alongside those tools
providing schemas so the agent knows what it can ask for
standardizing the client-to-capability boundary
MCP is not primarily about:
federating trust between independent gateways
explicit peer approval across operational domains
signed peer-to-peer message exchange
operator-visible federation state
That is incredibly useful. I think MCP is one of the most important protocol shifts in the current agent stack. But it is fundamentally about capability access.
And that is fine. MCP should not be forced to become the trust layer for everything.
If OGP is the walkie-talkie, MCP is the tool belt.
A2A: The Conference Call
A2A is closer to OGP in spirit because it is also about communication between agents rather than simple tool invocation.
Where A2A feels different to me is in its center of gravity.
A2A is optimized more around:
agent interoperability
capability discovery across agents
task exchange
status tracking
multi-agent cooperation on a shared workflow
That makes it a good fit for:
a research agent delegating fact collection to another agent
multiple agents participating in a shared task graph
heterogeneous agent frameworks needing a common handshake
That is a real problem. It is not OGP's problem.
OGP is not trying to become the universal agent mesh. It is trying to answer a narrower question:
When two gateways are run by different people or live in different operational environments, how do they establish trust and exchange messages in a way that stays explicit, revocable, and operationally sane?
If A2A is the conference call, OGP is the walkie-talkie clipped to your belt.
OGP: The Trust Layer
Open Gateway Protocol lives in a narrower and, I think, more operationally honest layer. It is not trying to be the universal app protocol for agents. It is not trying to replace your tool layer. It is not trying to absorb every workflow into a giant orchestration story.
It is trying to solve one problem well: trusted peer coordination across independent agent gateways
1. Federation Is Explicit
One gateway asks another: "Can we talk?" The other side approves or rejects. This is visible. Auditable. Revocable. Even when OGP uses convenience features like discovery cards or optional rendezvous, the trust relationship itself is still explicit.
2. Messages Are Signed
Every federated message carries Ed25519 signatures. That means identity is not a hand-wave. You can verify who sent the message and whether it was altered. If agents are going to act on each other's behalf across domains, this is not a nice-to-have. It's table stakes.
3. Delivery Is Targeted
OGP is not just "spray a message at some abstract agent cloud." In a real deployment, messages need to reach the right peer and the right local destination. Sometimes that means a particular agent. Sometimes it means a human-facing session or notification route. Sometimes it means falling back safely when the underlying platform cannot honor the ideal target precisely.
4. Boundaries Stay Intact
OGP does not try to merge your memory, tools, models, or infrastructure into a single shared platform. Each gateway keeps its own autonomy. That matters because the real world is full of partial trust: I want my work agent and personal agent to coordinate. I do not want them merged into one system. I want to approve that bridge explicitly. I want to revoke it later if needed.
5. The Operator Can See What's Going On
This is the part people underrate. OGP has to care about operator-visible state: who is federated, what policies exist, what recent activity happened, what gets approved, denied, or revoked. Why? Because the operator is the person who gets paged when something weird happens. Protocols that ignore this tend to look elegant in architecture diagrams and miserable in production.
The Operational Difference
This is where the differences stop sounding philosophical and start sounding practical.
MCP scenario
My agent wants to read a file or query a database. The capability is exposed via MCP. The agent calls it. Done.
A2A scenario
My research agent needs another agent to help complete a task. It discovers an agent, exchanges task context, and coordinates on status or outcomes.
OGP scenario
My personal agent on my laptop wants to ask my work agent on a VPS, "Did that deploy finish?" The gateways are already federated. The relationship was explicitly approved. The message is signed. The delivery path is tied to the right peer and local destination. If I want to revoke that bridge later, I can.
That is not just "agents talking."
That is cross-domain coordination with explicit trust.
Why Builders Keep Mixing These Up
The confusion is understandable because all three protocols participate in the same broader story: agents reaching outside themselves.
But "reaching outside yourself" is too broad to be a useful architecture category.
A better framing is:
That means a serious system can use all three:
MCP for tools
A2A for certain classes of agent workflow
OGP for federated trust, delivery, and peer coordination across gateways
These are not enemies. They are layers.
The Honest Narrowness
What I like about OGP is that it does not need to win by being bigger.
It wins, if it wins at all, by being narrower and more honest.
It does not try to:
replace your tool layer
become the universal agent mesh
swallow every workflow into a single platform
It tries to be:
The coordination layer for agents that live in different operational domains, with enough structure to be useful and enough friction to be safe.
That means it has to care about things that sound unglamorous but kill systems in production:
identity
approval
delivery
revocation
stale-peer cleanup
human visibility
These are not edge cases. These are the real job.
If your protocol only works when everyone shares one platform, one trust model, and one operator, it may be elegant. But it is not solving the messiest part of deployment.
OGP is trying to solve the messy part.
The Short Version
MCP
Use my tools
A2A
Coordinate agents on tasks
OGP
Federate trusted peers across gateways
Or, a little more precisely:
MCP is the tool layer
A2A is the interoperability layer
OGP is the trust-and-coordination layer
Pick the right lane.
Your future self, debugging something cross-domain at 2 AM, will thank you.
Coming Up Next
Next up: why the walkie-talkie model turns out to be more useful for real agent collaboration than the command-center fantasy.