MCP Explained walks through the 2025-11-25 protocol and attack cases
Original title: MCP Explained
The guide covers JSON-RPC shapes, deprecated batching, and defenses for tool poisoning, shadowing, and injection.
A Runlayer site, MCP Explained, walks through the Model Context Protocol specification dated 2025-11-25. It shows JSON-RPC requests, results, errors, and notifications, and marks batching and parts of sampling, transports, and authorization as deprecated. A separate section names attacks that are not in the spec, including tool poisoning, tool shadowing, token passthrough, prompt injection through tool results, and elicitation phishing. It also previews a 2026-07-28 spec and extensions such as Skills, Apps, and Server Cards.
- Every MCP message is described as JSON-RPC 2.0 over UTF-8 JSON.
- Batching of message arrays was deprecated on 2025-06-18.
- The 2026-07-28 draft would require resultType on every result.
- The next release is planned for March 2027, according to the page.
- Vendors
- Runlayer
- Products
- Model Context Protocol
From the original article
3 min read at mcp-explained.comAuthorization has deprecated partsOAuth 2. 1 for remote servers Skills over MCP beta extensionAgent Skills served by a server Spec 2026-07-28 ↗Stateless, no handshake, multi round-tripExtensions ↗Apps, Skills, Tasks, Server Cards, authSkills over MCP →Agent Skills as an MCP extension · lessonProgressive disclosure ↗Tool search and code mode, in the protocolRegistry ↗registry. modelcontextprotocol.
By rwilinski · mcp-explained.com
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