Microsoft Foundry has enhanced agent-to-agent collaboration with the general availability of the A2A Tool and A2A endpoints supporting protocol version 1.0. Existing integrations can still use the older a2a_preview tool and protocol version 0.3. Hosted Agents can access A2A tools through Foundry Toolboxes exposed via MCP. These features enable the creation of multi-agent systems where agents specialize, share skills, and cooperate securely across boundaries. A standardized A2A protocol eliminates the need for custom APIs or tightly coupled orchestration logic. Agents can now request assistance from others without intricate knowledge of their implementation details, using agent cards for discovery and the A2A protocol for communication. For Foundry-hosted A2A endpoints, discovery and endpoint access are secured by Microsoft Entra ID authentication. An external agent can discover and invoke a Foundry agent exposed as an A2A endpoint by interacting with its agent card and using the A2A protocol. Conversely, a Foundry agent can utilize the A2A Tool to connect to another A2A-compatible agent, configuring this through a RemoteA2A project connection. Hosted Agents integrate A2A capabilities by attaching a Foundry Toolbox, which then invokes the A2A Toolbox Tool and a RemoteA2A connection to interact with remote agents. Authentication emerges as a critical architectural decision, with options like none, custom-keys, oauth2, user-entra-token, project-managed-identity, and agentic-identity available for RemoteA2A connections, while incoming A2A endpoints strictly enforce Microsoft Entra ID authentication. To expose a Foundry agent as an A2A Endpoint, an agent card describing capabilities and the A2A protocol on the agent endpoint must be configured.