In the Model Context Protocol (MCP), the MCP client is the component that maintains communication between a host and an MCP server. The official documentation describes host, client and server as separate roles. The host coordinates the application, the client maintains the connection and the server provides data or functionality. Therefore, “MCP client” is not another name for the entire host nor for the server.
How it works
The host can create a client to connect to an MCP server. The client communicates with that server using the protocol and the configured transport. The architecture allows a compatible application to connect to different servers, without mixing the responsibility of coordinating the experience with the responsibility of providing a capability.
The official documentation describes stdio for communication between local processes and Streamable HTTP for HTTP based communication. These names identify transports, not architecture components. The choice depends on how the application and server are run. See the official MCP architecture documentation to see the roles and flows described by the protocol.
Through the client, the host can discover capabilities that the server announces, such as tools, resources or prompts, according to the implementation. The client is responsible for maintaining the technical interaction; the host application continues to control how the capabilities appear in the workflow. The protocol does not mean that every action will be executed without approval or that any connection is secure by default.
Practical example
Imagine a development application that needs to consult documentation for a library. The application is the host. An MCP client establishes the connection with a server that offers the documentation as a resource. The server provides the content, and the host decides how to present it to the assistant and the person programming.
In a diagram, the flow can be shown as “host, MCP client, MCP server”. If the connection is local, the documentation may indicate stdio; for a remote connection, it may indicate Streamable HTTP. The choice of transport does not change who coordinates the application nor who provides the resource.
If the server also offers a tool capable of changing data, the team should evaluate permissions and controls in the host. Identifying the client helps to describe the connection, but it does not replace the security review of the server and the actions available.
What it is for
The term helps to name precisely the part of the MCP architecture that maintains the connection. It is useful when documenting an integration, investigating communication errors or explaining a technical diagram. Questions like “what is the host?”, “which server is connected?” and “which transport was configured?” become clearer when the client is not confused with the other components.
To debug an integration, the team can check if the client starts correctly, if it can establish the connection, if it receives the list of capabilities and if it handles errors or interruptions in a understandable way. The specific behavior depends on the software used.
In summary, the MCP client is the communication bridge between host and server in the model described by the specification. To learn about the other end, see the entry on MCP server and the official documentation linked above.