--- title: "Model Context Protocol: what it is | Agent MCP Directory" description: "Model Context Protocol: A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts." canonical: https://agentmcpdirectory.com/standards/mcp site: "Agent MCP Directory" last_updated: 2026-11-05 section: "Standards" --- # Model Context Protocol: what it is | Agent MCP Directory > Model Context Protocol: A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts. Source: https://agentmcpdirectory.com/standards/mcp Site: Agent MCP Directory Last reviewed: 2026-11-05 # Model Context Protocol Model Context Protocol, maintained by MCP maintainers under the Agentic AI Foundation. A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts, and clients may offer elicitation. Status: Current revision 2026-07-28 (released 28 Jul 2026); prior revision 2025-11-25. Registry in preview with API v0.1 frozen since 24 Oct 2025. ## Fact sheet | Name | Model Context Protocol (MCP) | | --- | --- | | Maintainer | MCP maintainers under the Agentic AI Foundation | | What it is | A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts, and clients may offer elicitation. | | Status and version | Current revision 2026-07-28 (released 28 Jul 2026); prior revision 2025-11-25. Registry in preview with API v0.1 frozen since 24 Oct 2025. | | What it does not do | Does not grade servers, verify registry entries, or prescribe a .well-known discovery file in the 2026-07-28 core spec; server cards are still Working Group work. | ## Dated facts - The 2026-07-28 revision removes the initialize handshake and the Mcp-Session-Id header; every request carries protocol version and client capabilities in \_meta. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/changelog), dated 28 July 2026, read 4 November 2026) - Servers MUST implement server/discover to advertise supported versions, capabilities and identity. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/changelog), read 4 November 2026) - The standard transports are stdio and Streamable HTTP. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/basic/transports), read 4 November 2026) - HTTP+SSE is listed as a deprecated feature since 2025-03-26, with Streamable HTTP as its replacement. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/deprecated), dated 26 March 2025, read 5 November 2026) - The 2026-07-28 revision adds a feature lifecycle and deprecation policy with Active, Deprecated and Removed states and a minimum twelve-month deprecation window. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/changelog), read 4 November 2026) - MCP servers MUST implement OAuth 2.0 Protected Resource Metadata (RFC 9728); clients and authorization servers SHOULD support Client ID Metadata Documents. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/basic/authorization), read 4 November 2026) - Dynamic Client Registration (RFC 7591) is deprecated as a registration mechanism and kept for backwards compatibility. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/changelog), read 4 November 2026) - Clients MUST send the resource parameter (RFC 8707) in authorization and token requests and MUST validate a present iss parameter (RFC 9207). ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/basic/authorization), read 4 November 2026) - tools/list, prompts/list and resources/list results now carry required ttlMs and cacheScope fields. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/changelog), read 4 November 2026) - Roots, Sampling and Logging are deprecated in 2026-07-28. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2026-07-28/changelog), read 4 November 2026) - The 2025-11-25 revision added Client ID Metadata Documents, URL mode elicitation, icons and experimental tasks. ([modelcontextprotocol.io](https://modelcontextprotocol.io/specification/2025-11-25/changelog), dated 25 November 2025, read 4 November 2026) - The registry namespaces servers with reverse DNS or io.github. and verifies them by GitHub OAuth or OIDC, DNS or HTTP. ([github.com](https://github.com/modelcontextprotocol/registry), read 4 November 2026) ## Seen in the shared crawl | Path | Top 10,000 found | Ora leaderboard found | | --- | --- | --- | | /.well-known/mcp.json | 19 of 7,470 (0.25%) | 66 of 3,366 (1.96%) | A path counts only when the answer is the right kind of document. Many sites answer these paths with an ordinary web page, which is not counted. See [the census](https://agentmcpdirectory.com/census/). ## Compared with - [MCP vs A2A](https://agentmcpdirectory.com/compare/mcp-vs-a2a/) - [MCP vs WebMCP](https://agentmcpdirectory.com/compare/mcp-vs-webmcp/) - [NLWeb vs MCP](https://agentmcpdirectory.com/compare/nlweb-vs-mcp/) - [Agent Skills vs MCP](https://agentmcpdirectory.com/compare/agent-skills-vs-mcp/) - [CLIs vs MCP](https://agentmcpdirectory.com/compare/cli-as-agent-surface-vs-mcp/) - [OpenAPI vs MCP](https://agentmcpdirectory.com/compare/openapi-as-agent-surface-vs-mcp/) Edition 4 November 2026 Method [How rows are verified](https://agentmcpdirectory.com/method/) Data [CSV and JSON](https://agentmcpdirectory.com/data/) Markdown [This page as markdown](https://agentmcpdirectory.com/standards/mcp/index.md) ## Sources - [Model Context Protocol specification or home](https://modelcontextprotocol.io/specification/latest), read 4 November 2026 - [Model Context Protocol: modelcontextprotocol.io/specification/2026-07-28/changelog](https://modelcontextprotocol.io/specification/2026-07-28/changelog), read 4 November 2026 - [Model Context Protocol: modelcontextprotocol.io/specification/2026-07-28/basic/transports](https://modelcontextprotocol.io/specification/2026-07-28/basic/transports), read 4 November 2026 - [Model Context Protocol: modelcontextprotocol.io/specification/2026-07-28/deprecated](https://modelcontextprotocol.io/specification/2026-07-28/deprecated), read 5 November 2026 - [Model Context Protocol: modelcontextprotocol.io/specification/2026-07-28/basic/authorization](https://modelcontextprotocol.io/specification/2026-07-28/basic/authorization), read 4 November 2026 - [Model Context Protocol: modelcontextprotocol.io/specification/2025-11-25/changelog](https://modelcontextprotocol.io/specification/2025-11-25/changelog), read 4 November 2026 - [Model Context Protocol: github.com/modelcontextprotocol/registry](https://github.com/modelcontextprotocol/registry), read 4 November 2026 Last reviewed 5 November 2026