An enterprise agent can coordinate several specialists without turning every API call into another agent. That distinction is central to the Agent2Agent (A2A) protocol and the Model Context Protocol (MCP). In Microsoft’s updated AB-100 objectives, architects must understand open agent standards and select extensibility patterns that meet a real business requirement. MCP commonly exposes tools or resources for an agent to use; A2A supports delegation of tasks to another agent with its own processing and response. They solve related but different integration problems.<\/p>\n
Consider a customer service orchestrator that can check a subscription status, request an invoice PDF and ask a specialist agent to propose a payment-plan explanation. Subscription lookup and PDF retrieval are tool calls against authoritative services. The specialist can be modeled as an A2A agent if it genuinely owns a reasoning workflow and returns an accountable response. The solution still needs permission, consent, business-state verification and recovery regardless of which protocol carries the request.<\/p>\n
A tool performs a defined operation. It may retrieve a record, validate a field or create a proposed task. Its useful contract identifies the operation, parameters, side effects and expected result. An agent can interpret a broader task, choose its own supported operations and report progress or a result. Do not create an agent wrapper for a simple deterministic lookup merely because several teams are exploring multi-agent architecture.<\/p>\n
An A2A relationship is suitable when a remote agent provides a bounded specialized capability and the caller needs task-level collaboration. An MCP server is useful when several agents need a common interface to approved tools. Microsoft’s Copilot Studio A2A guidance<\/a> describes delegation to an external agent, while the MCP tool guidance<\/a> addresses tools and resources. Product support varies by experience and deployment, so use the documentation for the actual tenant and harness.<\/p>\n An inter-agent request should explain the desired outcome, allowed evidence, data boundary, deadline and shape of the answer. A billing specialist may be asked to produce a proposed explanation, not to approve a credit. The calling agent must preserve that distinction when it uses the specialist’s response. Define what counts as complete, partial, rejected or timed out. A natural-language sentence saying \u201cdone\u201d is not sufficient proof that an external system committed a business transaction.<\/p>\n Use a correlation identifier across all handoffs. When a customer disputes a recommendation, investigators should be able to reconstruct which agent was asked, what input was authorized, which knowledge version it consulted and what result came back. Avoid forwarding entire conversation histories by default. Send only the minimum facts and authority necessary for the delegated task, especially when the conversation includes another customer’s private details.<\/p>\n MCP can expose a changing set of tools. Dynamic discovery can reduce client integration work, but a new operation is also a new potential capability that requires review. Limit exposed tools to what the agent needs; validate descriptions and parameter schemas before production. A vague command such as perform_account_action is harder to govern than get_case_status or submit_refund_for_approval. The server must validate identity and business rules independent of the model’s request.<\/p>\n Microsoft documents selective MCP tool exposure<\/a> for Copilot Studio. Selection limits what the orchestrator can choose, but it is not a replacement for service-side authorization. If a tool becomes unavailable or changes its schema, define whether the client fails closed, requests a supported alternative or escalates. Quietly switching to a broader, more privileged tool can turn an availability problem into a security incident.<\/p>\n Authentication establishes the caller, but business authorization determines which data or operation the caller is entitled to access. An agent with its own workload identity must not automatically inherit the user’s complete permission set, and a user-delegated operation must not silently escalate to an administrator service account. Document the identity presented to each MCP tool and remote A2A agent, including tenant or organizational boundaries.<\/p>\n When a remote agent returns a proposed payment plan, the caller should not treat the response as a command to write financial records. Authoritative services must still check amounts, account ownership and approvals. A cross-organization integration should specify how long credentials and sensitive request data are retained. Microsoft’s A2A authentication guidance for Foundry<\/a> distinguishes supported authentication methods and the need to validate access.<\/p>\nDefine the task and its acceptance criteria<\/h2>\n
Treat discovery and tool schemas as controlled interfaces<\/h2>\n
Design identity and delegation without privilege inflation<\/h2>\n
Account for heterogeneous implementations and preview limits<\/h2>\n