What are an MCP client and host?
The host is the AI application (an IDE, a desktop chat app, a CLI agent); inside it, one MCP client holds the connection to each MCP server.
The host decides which servers are connected, shows tool calls to the user and asks for approval. Each client keeps a one-to-one session with its server, so a host with five servers runs five clients.
Clients can also offer features to servers, such as sampling (letting a server ask the host's model for a completion), roots and elicitation (asking the user for input), if the host supports them.
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Related terms
- MCP serverA program that exposes tools, resources or prompts to AI applications over the Model Context Protocol.
- Tool call (tools/list, tools/call)How an AI model uses an MCP tool: the client lists the server's tools with tools/list, the model picks one, and the client runs it with tools/call and returns the result to the model.