The Official MCP SDKs: Languages, Tiers and Versions

Status in the 2026-07-28 spec: not part of the protocol itself; SDK tiers are an official MCP community policy

The official MCP SDKs are ten libraries, maintained in the modelcontextprotocol GitHub organization, for building MCP servers and clients in TypeScript, Python, C#, Go, Rust, Ruby, Java, Swift, PHP and Kotlin. As of October 2026, six are Tier 1 (fully supported), Java is Tier 2 and Swift, PHP and Kotlin are Tier 3.

The tier tells you how complete the SDK is and how fast its maintainers promise to respond. It is the quickest way to judge whether an SDK is ready for production.

This page lists the SDKs, explains the tiers and gives each SDK's latest GitHub release, checked on 28 October 2026 against the official SDK page and each repository.

What the official SDKs are

An SDK (software development kit) handles the protocol plumbing: message formats, transports, version metadata and validation. You write the tools and data access. The SDK page says all official SDKs support creating servers, building clients, "local and remote transport protocols" and "protocol compliance with type safety."

You do not need an SDK to speak MCP. But the spec has many MUST rules, and a conformance-tested SDK gets most of them right for you. Our guide on how to build an MCP server shows the basics in Python and TypeScript.

Why tiers exist

Before tiers, it was hard to know whether a given SDK kept up with the spec. The SDK tiering system "establishes clear expectations for feature completeness, protocol support, and maintenance commitments." It was set up under SEP-1730, which the 2025-11-25 changelog lists among its governance updates. The tiering page says official tiering was published on 23 February 2026.

The tiers

Tier 1 SDKs include "all non-experimental features and optional capabilities like sampling and elicitation." The page adds: "Experimental features and protocol extensions (such as Tasks and MCP Apps) are not required for any tier."

Tiers are not permanent. An SDK can drop a tier if conformance tests on its latest stable release "fail continuously for 4 weeks," or if issues sit unaddressed for two months. The feature lifecycle policy also requires Tier 1 SDKs to mark deprecated features with their language's native deprecation tag. Our page on MCP versioning and deprecation explains that policy.

The ten SDKs as of October 2026

Tiers come from the official SDK page. Latest releases come from each repository's GitHub "latest release" on 28 October 2026.

A few details from the READMEs, checked on 28 October 2026:

• TypeScript. The main branch is "v2 of the SDK," with split packages @modelcontextprotocol/server and @modelcontextprotocol/client, "implementing the 2026-07-28 MCP spec." The older @modelcontextprotocol/sdk package (v1.x) gets bug fixes and security updates "for at least six months after the v2 release (2026-07-27)."
• Python. Installed with pip install "mcp[cli]" and requires Python 3.11 or later. Its docs include a "What's new in v2" guide and a migration guide.
• Go. The README's version table shows v1.7.0 and later targeting 2026-07-28 while still supporting older versions back to 2024-11-05.
• Rust. The README says it implements "the stable MCP 2026-07-28 specification" and stays compatible with 2025-11-25 and earlier.
• Swift. The README still describes the 2025-11-25 version as the one it implements.

On release day, the 2026-07-28 announcement said the four Tier 1 SDKs at the time (TypeScript, Python, Go and C#) supported the new spec, with Rust in beta. As of October 2026 the SDK page lists Rust and Ruby as Tier 1 too.

How an SDK maps to the spec

Here is the kind of message an SDK builds for you on every request, adapted from the Streamable HTTP transport page. In a Tier 1 SDK you never write this by hand:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "get_weather",
    "arguments": { "location": "Seattle, WA" },
    "_meta": {
      "io.modelcontextprotocol/protocolVersion": "2026-07-28",
      "io.modelcontextprotocol/clientInfo": { "name": "ExampleClient", "version": "1.0.0" },
      "io.modelcontextprotocol/clientCapabilities": {}
    }
  }
}

What changed across spec versions

• 2025-11-25: the SDK tiering system was established (SEP-1730). Our specification changelog lists the rest of that release.
• January to February 2026: conformance tests became available on 23 January, and official tiering was published on 23 February, per the tiering page.
• 2026-07-28: Tier 1 SDKs gained deprecation duties under the new lifecycle policy. The stateless change also meant a new major version for some SDKs, such as TypeScript v2.

Common mistakes

• Picking by popularity alone. Check the tier and whether the SDK targets 2026-07-28.
• Assuming extensions are included. Tasks and MCP Apps support is up to each SDK.
• Upgrading across a major version blind. TypeScript and Python both publish migration guides for v2. Read them, especially if you relied on sessions.
• Using community SDKs as if official. Only the repositories on the SDK page carry an official tier.
• Forgetting to recheck. Tiers move up and down; this table reflects 28 October 2026.

Next step

SDKs implement the core spec and, optionally, extensions. Learn how those optional add-ons work in how MCP extensions work. If you would rather have someone build on these SDKs for you, see our MCP development service, or browse the MCP specification hub.

Frequently asked questions