Agent-to-Agent (A2A) Communication and Multi-Agent Orchestration

What it does

Agent-to-agent (A2A) communication lets one agent hand tasks to another and get structured results back, rather than just calling an API. In Copilot Studio it's how a main agent orchestrates and delegates to other agents, first-party, second-party or third-party, sharing organisational context as it goes.

Key facts

A2A is an open standard (a2a-protocol.org) for communication and collaboration between agents, not a Microsoft-only protocol.
Copilot Studio connects to an external A2A agent by its endpoint URL; if the agent publishes a valid agent card at the standard .well-known path, Copilot Studio pulls its name and description automatically.
Unlike a plain HTTP connector, A2A is built for agent workflows: multi-turn interactions, rich contextual metadata and interoperability across frameworks.
A2A messages carry a contextId, message IDs, locale and the full chat history, not just the latest utterance, so the receiving agent has real context.
Authentication options are None, API key or OAuth 2.0.
Copilot Studio offers parallel integration paths: A2A for external framework agents, MCP servers for MCP tools and resources, the Activity Protocol for Microsoft 365 Agents SDK agents, and custom connectors for plain APIs. You can combine several in one agent.
A2A moved to general availability as a platform-level capability in the 2026 Release Wave 1, alongside Fabric Data Agent integration and Microsoft 365 Agents SDK orchestration.
MCP and A2A are complementary, not competing: MCP standardises how agents reach tools and data, A2A standardises how agents talk to each other.

When to use / skip

Use A2A when you want to delegate to an agent that already speaks the protocol, is built on an external framework or hosted outside Copilot Studio, and has its own domain reasoning. If you only need to call an API or hit a basic HTTP service, use a custom connector; if you need tools and resources, use an MCP server; if the other agent is built on the Microsoft 365 Agents SDK, use the Activity Protocol. Reaching for A2A to wrap a simple API is over-engineering.

Configuration decisions

Pick the right integration model per connection: A2A, MCP, Activity Protocol or custom connector. They're not interchangeable.
Decide the authentication method (None only for samples; API key or OAuth 2.0 for anything real) and secure the endpoint.
Write clear agent metadata (name and description), since that's what the orchestrator uses to decide when to delegate.
For on-premises or VNet-hosted A2A agents, note that A2A connections ride the custom connector infrastructure, so the same networking rules apply.
Agree how much of the A2A payload metadata (context, history) the external agent is allowed to see and retain.

Gotchas

You own the risk of any external agent you connect: data flows, quality, permissions and observability are your responsibility, and Microsoft says so explicitly.
The full chat history travels in the payload, so delegating to a third-party agent can share more context than people expect; check it's appropriate.
Weak or vague agent descriptions lead to bad routing decisions by the orchestrator; treat metadata as load-bearing.
The integration-model choices look similar in the UI but behave differently; picking the wrong one is a common early mistake.
This space changed quickly through 2025 and 2026; confirm current GA status and limits before you design a multi-agent topology.

Consultant notes

Frame A2A as the interoperability play: it's how a client's agents talk to agents they didn't build, including across vendors, without bespoke glue.
Tie it to Work IQ for the context story, agents delegate with shared organisational context rather than starting cold, which is the differentiator over raw API calls.
Governance is the hard part, not the wiring. Multi-agent means multi-owner; push clients to sort identity, traceability and human oversight before they scale it.
Keep MCP and A2A distinct in client conversations: tools versus agents. Conflating them muddies both the architecture and the risk picture.

Before connecting any third-party A2A agent, confirm what's in the payload (it includes full chat history) and who's accountable for the external agent's behaviour.