What is the Model Context Protocol (MCP)?

How it works

Anthropic released MCP as open source on November 25, 2024. The company presented it as one shared protocol to replace the custom integration that each new data source otherwise requires. It credited MCP's creation to David Soria Parra and Justin Spahr-Summers.

The specification defines three roles. A host is the AI application, such as a chat assistant or a coding tool. Clients are connectors inside the host. The architecture document says each client talks to exactly one server. Servers are programs that supply context and capabilities. Messages use JSON-RPC 2.0, an existing format for one program to send requests to another. Servers can offer three kinds of features:

• resources (data for the user or the model)
• prompts (reusable message templates)
• tools (functions the model can ask to have run)

Why it matters

The aim of a shared protocol is that a connector written once can work with many AI products. TechCrunch reported on March 26, 2025, that OpenAI chief executive Sam Altman said the company would add MCP support across its products, starting with its Agents SDK. On December 9, 2025, the Linux Foundation announced that Anthropic was contributing MCP to a new Agentic AI Foundation. It said platinum members at launch included Amazon Web Services, Google, Microsoft and OpenAI. The announcement counted more than 10,000 published MCP servers.

The specification flags security risks. It states that tools amount to arbitrary code execution and that hosts must obtain explicit user consent before invoking one. It adds that the protocol cannot enforce these principles itself, leaving them to the applications that implement it.

Where things stand in 2026

As of October 2026, the project's versioning page lists 2026-07-28 as the current revision. Revisions are identified by date. The maintainers' release post of July 28, 2026, says this revision makes the protocol stateless. It says the opening handshake and session identifiers are gone. Each request carries its own version and capability details, it says, so any server instance can answer it. The specification also lists optional extensions, among them Tasks for long-running operations and MCP Apps for interactive interface elements. The post put downloads of the project's Tier 1 software development kits at close to half a billion a month.

The change list also marks three features, Roots, Sampling and Logging, as deprecated, with a deprecation window of at least twelve months.