MCP Explained
The mcp-explained.com site has published an interactive guide to the Model Context Protocol (MCP). Its approach is to trace each JSON-RPC message the protocol sends, in order, and its topics include transports, OAuth, tools, resources, sampling, elicitation, tasks, tool search and codemode. The guide defines three roles: the host is the AI app, such as Claude, Cursor or ChatGPT; the server is a small program that exposes tools, data or prompts; and the model picks what to use but never contacts a server directly. It also argues that MCP is not REST: messages run as JSON-RPC over stdin/stdout or a single HTTP endpoint, and servers can send requests back.
The timing is relevant because the protocol itself changed this summer. The maintainers finalized the 2026-07-28 specification on July 28, after a release candidate locked on May 21. They describe it as the largest revision since launch. The main change removes protocol-level sessions, so each request carries its protocol version, client identity and capabilities in a metadata field. According to The Register, servers on the new revision may not work with older clients, and the reverse may also hold.
Why it matters
For teams building agent products, the July revision changes deployment economics. Under the stateless design, a remote MCP server can run like any other HTTP service, according to the maintainers, so it can sit behind the same load balancers and hosting used for conventional APIs. Companies that built session-based integrations will need a migration plan, since the new revision may not work with older clients.
For investors and sellers, the adoption figures are the more visible signal. Wikipedia reports more than 10,000 MCP servers deployed in production by mid-2026 and SDK downloads above 97 million per month. Governance moved to the Linux Foundation's Agentic AI Foundation in December 2025, which lowers the risk that one vendor controls the standard. Reports differ on download volume: a Pinnasys analysis puts monthly downloads near half a billion, so buyers should check the basis of any figure before using it in a pitch.
Key points
- 1The mcp-explained.com guide traces each JSON-RPC message and covers transports, OAuth, tools, sampling and tasks.
- 2The 2026-07-28 MCP specification was finalized on July 28, 2026, after a May 21 release candidate.
- 3The revision removes protocol-level sessions and moves version and capability data into each request.
- 4Tasks for long-running operations moved out of the core protocol and into an extension.
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