2026 update: MCP's biggest spec change yet, and where Agent Skills now work
On 28 July 2026 MCP shipped a spec its own team calls the most substantial change since authorization was added — the handshake is gone, only two transports remain, and sampling, roots and logging are deprecated. Here is everything that changed in 2026, plus a support table we checked ourselves.
What the 2026-07-28 spec changed
The current spec is 2026-07-28 (previously 2025-11-25). The MCP team describes it as “the most substantial changes we have made to the specification, probably since adding authorization.”
| Change | Detail |
|---|---|
| The handshake is gone | No more initialize/initialized and no Mcp-Session-Id header — every request carries its own protocol version and client capabilities in _meta |
| New capability discovery | A mandatory server/discover RPC replaces the old handshake |
| Only two transports | stdio and Streamable HTTP — that is the complete list now |
| New required headers | Streamable HTTP requires Mcp-Method and Mcp-Name so gateways can route without parsing the JSON body |
| Caching | List and resource-read results now carry ttlMs and cacheScope |
| Full JSON Schema | inputSchema/outputSchema are now full JSON Schema 2020-12 |
| Hardened auth | Mandatory iss validation (RFC 9207), OIDC alignment, and a shift from Dynamic Client Registration to CIMD |
Backward compatibility: servers on 2026-07-28 may not work with older clients and vice versa — both sides need to share an era or implement a fallback. The TypeScript, Python, Go and C# SDKs are updated; Rust is still in beta.
What is being retired (deprecated, not removed yet)
2026 also brought MCP's first feature lifecycle policy, guaranteeing at least 12 months between a deprecation and any removal.
| Feature | Deprecated | Earliest removal |
|---|---|---|
| Roots | 2026-07-28 | on/after 2027-07-28 |
| Sampling | 2026-07-28 | on/after 2027-07-28 |
| Logging | 2026-07-28 | on/after 2027-07-28 |
| Dynamic Client Registration | 2026-07-28 | on/after 2027-07-28 |
| HTTP+SSE transport | 2025-03-26 | 3 months after SEP-2596 is final |
Elicitation — asking the user a question mid-run — is now the only client feature left in the core spec.
2026 also introduced an extensions framework: independently versioned, always opt-in. The official ones are MCP Apps, MCP Tasks, OAuth Client Credentials and Enterprise-Managed Authorization.
Which AI supports MCP and Agent Skills (checked against vendor docs)
Worth knowing: MCP's official client matrix no longer exists — the old link now redirects to the homepage. We checked each vendor's own documentation on 29 July 2026.
| Client | MCP | Agent Skills | One-click install |
|---|---|---|---|
| Claude Code | ✓ | ✓ .claude/skills/ | Via /plugin (not a GUI) |
| Claude Desktop | ✓ | ✓ | ✓ .mcpb bundles |
| Claude web/mobile | ✓ (remote only) | ✓ | ✓ Connectors |
| ChatGPT / Codex | ✓ | ✓ .agents/skills | ✓ (web) |
| Cursor | ✓ | ✓ .agents/, .cursor/skills/ | ✓ Marketplace |
| GitHub Copilot | ✓ | ✓ .github/skills | ✓ MCP Registry |
| VS Code | ✓ (most complete) | ✓ | ✓ @mcp |
| Gemini CLI | ✓ | ✓ ~/.gemini/skills/ | — |
| Antigravity | ✓ | Not documented | ✓ MCP Store |
| Windsurf (now Devin Desktop) | ✓ | ✓ | ✓ Plugin Store |
| Zed | ✓ | ✓ ~/.agents/skills/ | ✓ Extensions |
| Cline | ✓ | ✓ | Via wizard |
| JetBrains Junie | ✓ | ✓ .junie/skills/ | ✓ Install Assistant |
VS Code is the most complete MCP client we could verify — the only one whose docs cover sampling, elicitation and roots together.
For how far each tool can actually run a job, see Supported AI.
Agent Skills in 2026 — the spec stood still, everything around it moved
The spec itself barely changed. Frontmatter still has exactly six fields: name and description (both required), plus license, compatibility, metadata and allowed-tools (still Experimental). There is no version field, and the spec itself carries no version number or changelog.
The portability caveat: “SKILL.md is portable” holds only for name + description + the markdown body. Claude Code documents 17 additional frontmatter fields that are its own (model, effort, context: fork, hooks, argument-hint and more) — other tools will not understand them.
agentskills.io is not a place to download skills — it is a spec page plus a showcase of supporting products (44 today). Its own contributing guide says the team does not maintain a community skill directory.
The genuinely new 2026 convention is the shared .agents/skills/ folder that most clients agreed to read — a convention, not part of the spec.
Also new: MCP formed a Skills Over MCP Working Group (interest group in February 2026, promoted in April) with Google, GitHub, AWS, Bloomberg and Databricks participating, aimed at carrying Skills over MCP.
New to Skills? Start with What are Agent Skills or browse the Skills library.
AGENTS.md joined the Linux Foundation — but Claude Code still does not read it
OpenAI donated AGENTS.md to the Agentic AI Foundation under the Linux Foundation (announced 9 December 2025), alongside Anthropic's MCP and Block's goose. Over 60,000 open-source projects now use AGENTS.md.
One catch worth knowing: Claude Code reads CLAUDE.md, not AGENTS.md — its documentation states this outright. Anthropic's own recommended workaround is a single import line in CLAUDE.md:
@AGENTS.md
A symlink also works, but on Windows that needs Administrator rights or Developer Mode, so the import line is the easier route.
New on the Claude Code side this year: a .claude/rules/ folder with glob-scoped paths: rules, claudeMdExcludes for monorepos, and an automatic memory system.
For ready-made rule files, see the Rules library.
One-click install today
.mcpbbundles (formerly.dxt) — drop into Claude Desktop at Settings → Extensions · note: the repo has shipped no releases through 2026, but there is no deprecation notice either — treat it as quiet, not dead- Cursor Marketplace — Add to Cursor with OAuth-authenticated install
- VS Code — install from Extensions via
@mcp, or runcode --add-mcp - Antigravity MCP Store — in-IDE panel with 60+ integrated servers
- JetBrains Junie — an assistant that searches the MCP registry and fills in the config
- Claude Code —
/pluginagainst a marketplace · one plugin can bundle skills, agents, hooks and.mcp.json
The official MCP Registry is still in preview, not GA, and the team says it is meant for downstream aggregators rather than direct use by host apps.
One more change that affects daily use: Claude Code merged slash commands into Skills — both .claude/commands/deploy.md and .claude/skills/deploy/SKILL.md now produce /deploy. Existing command files keep working.
2026 timeline
| Date | What happened |
|---|---|
| 9 Dec 2025 | Agentic AI Foundation formed under the Linux Foundation — MCP, goose and AGENTS.md donated |
| 18 Dec 2025 | Agent Skills published as an open standard at agentskills.io |
| 26 Jan 2026 | MCP Apps — the first official extension, production-ready on Claude, Goose, VS Code and ChatGPT |
| 1 Feb 2026 | Skills Over MCP interest group formed (promoted to a working group on 16 April) |
| 29 Apr 2026 | Google Cloud Next '26 — 50+ Google-managed MCP servers (BigQuery, Cloud Run, Gmail, Drive, Maps and more) |
| 18 Jun 2026 | Enterprise-Managed Authorization goes stable — one login across every connected MCP server |
| 28 Jul 2026 | The 2026-07-28 spec goes final — adopted immediately by AWS Bedrock, Cloudflare Workers, Google Cloud, Microsoft Foundry and Netlify |
What you should actually do
- Nothing urgent. Everything deprecated stays for at least another year.
- If you build MCP servers, stop relying on sampling, roots and logging now, and move from HTTP+SSE to Streamable HTTP.
- If you publish Skills, stick to the six standard fields for real cross-tool portability, and ship them in
.agents/skills/. - If you mix Claude Code with other tools, write your rules once in
AGENTS.mdand add@AGENTS.mdtoCLAUDE.md. - If you just use AI, there is nothing to do — pick from the MCP library and Skills library, which we curate and freshness-check.