An AI application may need information from a document system or an action from a business service. Each integration needs a shared way to request that information or action.
The MCP specification defines that shared interface. A compatible client can discover the capabilities a server exposes. The application still needs permission to use protected capabilities.
What are the host, client and server?
The host is the AI application. The client is its connector. The server is the program supplying capabilities.
The specification's roles separate the application from the connector inside it.
| Role | Responsibility | Example |
|---|---|---|
| Host | Coordinates the AI interaction and its connections | An assistant application |
| Client | Exchanges protocol messages with an MCP server | A connector inside that application |
| Server | Exposes context or callable operations | A program providing access to documents |
A host can use several clients to connect to different servers. The architecture guide describes one client for each server connection.
How do the messages travel?
The standard transports carry messages through local process streams or HTTP.
The transport specification defines both:
- Stdio: the client launches a server process and exchanges messages through its input and output streams.
- Streamable HTTP: a server receives HTTP requests and can stream messages back to clients.
A server therefore need not be a remote website. It can be a program running on the same machine as the client.
The transport carries the exchange. Account permissions still require authorization. The MCP OAuth answer explains authorization for protected HTTP servers.
Is MCP an agent framework?
MCP defines an integration protocol rather than a framework that runs an agent's reasoning and task loop.
The architecture guide's scope leaves how applications use models and manage context to those applications. The host chooses how to use the information and operations available through its connections.
A protocol connection alone does not decide which action completes a user's task.
Does MCP replace an API?
MCP can expose an API's operations through a separate protocol interface. The underlying API can continue carrying out those operations.
The architecture guide's tool example shows an MCP server executing a requested tool. The implementation behind a tool can call another service.
For example, a hypothetical order-status tool could retrieve an order through an existing API. MCP describes the client-server exchange. The order service still owns its records and access rules.
The primitives answer explains tools, resources and prompts. The A2A comparison covers communication between agents.
How do I use MCP with Bird?
You can connect an AI client to Bird's MCP server.