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Glossary

Model Context Protocol (MCP)

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Definition

The Model Context Protocol (MCP) is an open standard for connecting AI applications to external systems such as data sources, tools and workflows.

Also called: MCP, MCP server, MCP connector.

Anthropic introduced MCP in 2024 and it's now supported by many AI apps and developer tools. Its own site compares it to a USB-C port: build a connection once, and any MCP-compatible app can use it.

PartRole
Hostthe AI application, e.g. Claude Code or Codex
Clientthe connection the host keeps to one server
Servera program that exposes tools (actions), resources (data) and prompts (templates)
Transportstdio for a local server process, or HTTP for a remote one

For coding agents, MCP servers add things like issue trackers, databases, design files or a browser. Claude Code adds them with claude mcp add or a project's .mcp.json; Codex lists them in its config.toml. An MCP tool acts with whatever access you give the server, so only add servers you trust, and remember that each tool's definition takes up some of the model's context.

In Pairbar

Pairbar doesn't manage your MCP servers; your Claude and Codex setups stay as they are. It has one optional server of its own: Pairbar's tools, tools a Claude or Codex chat can call to see its project's chats, tasks, skills and limits, or to ask for agent actions that run only once you allow or approve them, installed only when you click Install in Settings → Integrations. Where Pairbar limits access on purpose is in workflows: the planner, the goal check and the doctor run on Claude with only Read, Glob and Grep (no commands, no MCP servers), and on Codex in the read-only sandbox. See Describe it, and AI plans it.

Frequently asked questions

Who created MCP?
Anthropic introduced the Model Context Protocol in 2024 as an open standard; it's developed in the open at modelcontextprotocol.io.
Do Claude Code and Codex both support MCP?
Yes. Both can connect to MCP servers, configured separately in each tool.
Does Pairbar need MCP?
No. Pairbar reads the apps' local files and uses their command-line tools. Its own MCP server (Pairbar's tools for Claude and Codex, mostly read-only, with agent actions you approve) is optional and off until you install it; see the MCP server glossary entry.

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