Model Context Protocol - Architecture

Type: official-doc Tier: 1 (Official Doc) Author(s): Model Context Protocol Date: 2025-06-18 URL: https://modelcontextprotocol.io/specification/2025-06-18/architecture Accessed: 2026-06-02

Why This Source Matters

This is the primary source for MCP's architecture. It establishes the provider/consumer split that the curriculum does not teach through hand-wired tools alone: a host coordinates clients, each client connects to one server, and servers expose focused capabilities without owning the whole application loop.

Key Claims

• MCP follows a client-host-server architecture: the host manages multiple client instances, each client maintains an isolated session with a server, and each server provides specialized context or capabilities.
• MCP is built on JSON-RPC and uses stateful sessions with capability negotiation.
• Servers expose resources, tools, and prompts as MCP primitives.
• Hosts enforce security policies, consent requirements, lifecycle, and context aggregation.
• Servers should be focused and composable; a server should not see the whole conversation or see into other servers.
• Capability negotiation declares which features are available during a session, such as tools, resources, prompts, subscriptions, or sampling.

Relevant To

• concepts: [mcp, provider-consumer-split, client-host-server, capability-negotiation, protocol-interface]
• projects: [06-ai-coding-copilot, 08-ai-agent, 09-personal-learning-os, elective-mcp-interface-layer]

Notes

This source grounds MCP as an interface protocol, not an agent framework. It should be used to distinguish a hand-wired Python tool loop from a reusable protocol surface that multiple hosts can consume.