These three terms appear in tech news and in vendors' sales emails. Here is what they mean, based on each project's own documentation as read on 28 October 2026.
MCP: the Model Context Protocol
The project's introduction describes MCP as an open-source standard for connecting AI applications to external systems: data sources, tools and workflows. It compares MCP to a USB-C port: one standard way to plug things in. See What is the Model Context Protocol?
For a business: if your booking system offers an MCP "server", an assistant that supports MCP can ask it for available times or make a booking, in a standard way, instead of reading your web page. Think of it as a door built for software.
A2A: the Agent2Agent protocol
The A2A project describes itself as an open standard that lets AI agents communicate and collaborate with each other, even when built with different frameworks or by different vendors. It says A2A complements MCP: MCP connects an agent to tools and data, while A2A is for agents working with other agents. See the A2A Protocol site.
For a business: a customer's personal agent might talk to a business's agent, for instance one that handles your bookings, using A2A. You would only meet this if you use a tool that exposes an agent.
Agent card
In A2A an agent card is a JSON document describing a remote agent: its identity, service address, supported features, authentication needs and skills. It is typically published at a standard address on the agent's domain, /.well-known/agent-card.json, as described in the A2A project's page on agent discovery. Think of it as a business card for software.
For a business: an agent card tells other agents what your agent can do and how to ask. It does not set your booking rules by itself.
How the three fit together
- A customer asks their assistant to book something.
- The assistant finds your business and looks for a way to deal with it: your web page, your phone, or a software interface.
- If you have an MCP server or an A2A agent with a card, the assistant can use it in a standard way.
- If not, it falls back to reading your pages or telling the customer to contact you.
Do you need to do anything?
- Probably not directly. You should not have to write any of this yourself. Ask your booking-system vendor whether they support these standards.
- Do the basics anyway. Plain-text prices and hours, a booking link and written terms matter whether or not any protocol is involved. See why assistants often cannot book a salon.
- Be wary of hype. Standards are young and change. No protocol guarantees customers.
- Ask about control. If a tool exposes your business to agents, you should be able to set rules, see what happened and switch it off.
Questions to ask a vendor who mentions these
- Which of these do you support today, not on a roadmap?
- What can an agent do through it: read only, or also book and cancel?
- Where do I set my rules, and are they enforced?
- How do I see what agents did?
- Which assistants actually use it today?
For the booking side in practice, see what an AI agent booking is.