# Client

The software that opens the connection and makes the call, to a model or to an MCP server.

A role, not a product: ChatGPT with no tools is still a client. Because every AI tool contains a client, the word doesn't tell ChatGPT, Claude Desktop, Claude Code, Codex and OpenCode apart. What separates them is the harness around the model. In MCP's own terms, the app (Claude Desktop, ChatGPT) is the host, and the client is the piece inside it that holds the connection to one MCP server. Not to be confused with the business sense of a customer.

Kind of: Agent harness

Source: https://redfinchadvisory.com/lexicon/client (version 1.0, changed 2026-10-21)