iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
To connect .NET agents with A2A, a client resolves a remote agent’s Agent Card and wraps the endpoint as a familiar AIAgent. An ASP.NET Core host does the reverse: it registers a local agent, adds the A2A server, maps one or both protocol bindings, and publishes the card. A2A earns its overhead only when an agent call crosses a process, service, team, or organizational boundary. For agents that share one application and one team, the framework’s in-process agent-as-tool pattern is simpler and cheaper.
When should I use A2A instead of in-process agent tools?
A2A is the network protocol boundary. It standardizes how remote agents discover one another, exchange messages, and coordinate tasks. In Microsoft’s Agent Framework, a .NET client can wrap a remote A2A agent as an ordinary AIAgent, and an ASP.NET Core host can expose a local agent through A2A endpoints.
Use A2A when one agent must call another across a process, service, team, organizational, or framework boundary, or when the two agents need independent deployment and release cycles. The protocol lets the remote agent keep its memory, tools, and implementation opaque to the caller, and that opacity is the main reason to accept the extra cost. When the agents run in one process under one team, the in-process agent-as-tool pattern is the simpler choice.
| Decision axis | In-process agent composition | A2A remote-agent composition |
|---|---|---|
| Boundary | Same application or process, typically the same team | Crosses a process, service, team, or organizational boundary |
| Interoperability | Often tied to framework or runtime integration | Protocol-based across conforming frameworks and languages |
| Latency | Lower; no network hop | Adds HTTP and network latency to every call |
| Operations | Follows the application’s own lifecycle | Requires service reliability, timeout and retry handling, versioning, and remote state planning |
| Discovery | Application wiring | Agent Card, registry or catalog, or a directly configured endpoint |
Because every A2A call is an HTTP request, keep high-frequency or latency-sensitive steps local, even when they belong to a separate agent conceptually.
#1 Best Overall
Where orchestration policy belongs
A2A lets agents communicate and delegate, but it does not define an execution order by itself. If a workflow needs explicit graph-based sequencing, shared state, and recoverability, add a workflow or orchestration layer on top of the agents. Microsoft points to explicit graph-based workflows for those requirements rather than expecting the wire protocol to carry the whole workflow.
What is the difference between A2A and MCP?
The official A2A Protocol documentation describes the two as complementary. MCP standardizes how an agent connects to tools, APIs, and resources. A2A lets independent agents discover one another, delegate work, and exchange results. A common layout therefore uses MCP inside each agent for its own tools and A2A between agents for delegation.
How the client, server, and Agent Card fit together
Every A2A exchange has a client side and a server side. The client holds a reference to a remote agent and calls it through the standard AIAgent methods. The server hosts a local agent and publishes the endpoints that make it reachable. Both sides agree through the Agent Card. The official A2A Protocol overview opens with this sentence: “The Agent2Agent (A2A) Protocol is an open standard for seamless communication and collaboration between AI agents.”
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
An Agent Card is the discovery contract. It describes the agent’s metadata and the interfaces it supports, so a client can see what the agent offers and select an endpoint and binding the server actually implements. Each card carries:
- Name and description
- Version
- Supported input and output modes
- Supported endpoint URL
- Protocol binding
- Protocol version
Update the card in the same release that changes an interface or version. A stale card sends clients to an endpoint or binding that no longer answers. In .NET, the documented well-known location is /.well-known/agent-card.json.
How do I connect .NET agents with A2A?
The client side ships in the Microsoft.Agents.AI.A2A NuGet package. Microsoft Learn’s client documentation shows it installed with:
dotnet add package Microsoft.Agents.AI.A2A --prereleaseThe package is still prerelease and its APIs change, so confirm the current version on NuGet before you pin it. Microsoft’s A2A documentation showed a last-updated date of 25 August 2026 when reviewed, so check it for later changes as well.
Get an AIAgent through one of three discovery paths
- Well-known Agent Card: create an
A2ACardResolverfor the remote host, retrieve its Agent Card, and create theAIAgentwithGetAIAgentAsync(). - Catalog or registry: if an enterprise catalog already returns an
AgentCard, convert that card into anAIAgent. - Direct endpoint: create an
A2AClientfor a known URI and adapt it to anAIAgentwith a name and description you choose.
The discovery path follows from who controls discovery. A well-known card suits a host your team operates. A catalog suits an organization that already maintains a registry of agents. A direct endpoint suits a fixed integration with one known remote service, but the caller then hard-codes the location.
Call the remote agent
The wrapper exposes the standard RunAsync and RunStreamingAsync methods, so application code does not need to own the remote implementation. Streaming is carried as Server-Sent Events over HTTP+JSON.
The wrapper does not expose the remote agent’s tools as local tools. To change what the remote agent can do, change its configuration on the server that hosts it.
Handle long-running work and conversation continuity
For work that outlasts one request, Microsoft documents background responses that return a continuation token. The client can poll with that token or reconnect to an interrupted stream. If later turns must continue the same remote conversation, keep the session or context identity from the earlier turn and send it with the next call; otherwise the new call may not continue the earlier exchange.
How do I expose an ASP.NET Core agent over A2A?
The server side uses the Microsoft.Agents.AI.Hosting.A2A.AspNetCore package, which includes the core hosting logic. Microsoft’s example uses Microsoft Foundry and Azure identity for its model and provider setup. Those are example choices, not protocol requirements, so use the provider and identity approach your environment already relies on.
- Build the agent with your usual .NET agent configuration and register it in dependency injection under a key.
- Register the A2A server for that key. Microsoft’s example calls
AddA2AServer("agent-name"). - Map one or both protocol bindings with
MapA2AHttpJsonand/orMapA2AJsonRpc. The binding table below describes each one. - Publish the card with
MapWellKnownAgentCard, using the fields described in the Agent Card section, so the endpoint URL, binding, and protocol version match what you mapped in step 3. - Put the endpoints behind the authentication and network controls your environment requires.
- Replace the default
InMemoryAgentSessionStoreandInMemoryTaskStorewith durable implementations before production, as explained in the production section below.
Choose the binding clients will call
| Binding | Server method | Wire format | Streaming |
|---|---|---|---|
| HTTP+JSON | MapA2AHttpJson |
Ordinary HTTP requests and responses | Server-Sent Events |
| JSON-RPC 2.0 | MapA2AJsonRpc |
JSON-RPC 2.0 over HTTP | Not stated in Microsoft’s A2A hosting documentation |
A client can express preferred bindings, but it can use only a binding the server supports. Map every binding you advertise on the card. Each host can publish one Agent Card at the well-known path. Other agents on the same host can still be called directly or found through a separate discovery mechanism.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.State, reliability, and security before production
Replace the default in-memory stores
The default InMemoryAgentSessionStore and InMemoryTaskStore are intended for development. Session and task state disappears when the process restarts, and it is not shared between service instances. That is acceptable for a local prototype and unsuitable for a production service. The gap matters most when you enable background tasks or run more than one instance, because a polling client may reach an instance that does not hold its task. Register durable implementations before either of those changes reaches production.
Plan for remote failure
A remote agent is a distributed service, so design for these conditions:
Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →- Network timeouts on every call, sized to the work the remote agent performs.
- A retry policy for transient errors. Retries can repeat work that already ran, so decide which tasks are safe to repeat.
- Version compatibility between the protocol version on the card and what your client expects.
- Health monitoring for each remote endpoint.
Treat remote agents you do not operate as untrusted input
Validate the Agent Card, messages, artifacts, and task statuses from any remote agent you do not control before your application acts on them. The remote agent controls its own state, and your code sees its responses rather than its internal reasoning, so check the fields that drive your decisions at the boundary.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
