MCP (Model Context Protocol)

MCP — the Model Context Protocol — is an open standard for exposing tools, resources, and prompts to agentic harnesses. Introduced by Anthropic in late 2024 and adopted broadly across the ecosystem, MCP gives any harness (Claude Code, Cursor, Cline, Windsurf, and others) a consistent way to discover and call external capabilities provided by independent servers.

An MCP server advertises three kinds of surface: tools (callable functions the model can invoke), resources (readable data the harness can attach to context — files, records, documents), and prompts (reusable prompt templates). A harness acts as the MCP client, connecting to one or more servers over stdio or HTTP and surfacing their capabilities to the model as regular tool calls.

The win is composability. Before MCP, every harness had to ship its own integrations for GitHub, Linear, Postgres, Slack, filesystem, browser automation, and so on. With MCP, an organization can stand up a single MCP server for each internal system — or pull one off the shelf — and every compliant harness can use it without custom code. It is roughly analogous to LSP (Language Server Protocol) for IDEs: a standard plug for a fragmented market.

For agentic systems, MCP is the cleanest way to extend an agent's scope without modifying the harness. It is also how many products compose across vendors — a Cursor user can use the same MCP server a teammate uses from Claude Code.