Tc39 MCP

📖 Docs: mcp.xyzzylabs.ai/tc39 - Get started · Tools · Cookbook · Editions · Architecture · Hosting

People connecting this server to Claude, Cursor, VS Code, or another MCP client. The project is written in TypeScript.

VERIFIED ACTIVE

LAST COMMIT 2026-08-25 · ★ 2 · #240 OF 848 MAINTAINED OTHER · VERIFIED 2026-08-25

MIT · TypeScript servers · how we verify → /methodology

01 · Install Tc39 MCP

before you install - you'll need

Set TC39_MCP_BASE_URL before connecting.

Claude Code

claude mcp add xyzzylabs-tc39-mcp --transport http https://mcp.xyzzylabs.ai/tc39/mcp

Claude Desktop / Cursor / VS Code - add to config

{
  "mcpServers": {
    "xyzzylabs-tc39-mcp": {
      "url": "https://mcp.xyzzylabs.ai/tc39/mcp"
    }
  }
}

Same JSON for Cursor. For VS Code, rename the top-level key from `mcpServers` to `servers`.

Using another client? Same JSON, different key

Claude Desktop · mcpServers

Cursor · mcpServers

VS Code · servers

Windsurf · mcpServers

Zed · context_servers

Cline · mcpServers

Roo Code · mcpServers

Continue · mcpServers

LibreChat · mcpServers

Gemini CLI · mcpServers

Codex CLI · mcp_servers

Full setup guides: every client.

02 · Evidence

https://mcp.xyzzylabs.ai/tc39/mcp

transport: streamable-http

endpoint alive - responded to MCP initialize · probed 2026-08-25

Security posture

What to check before giving this server access to your agent - from the registry, GitHub, and our own probes. We don't score safety; we show what's verifiable.

runs as local process (stdio) - runs on your machine with your user's permissions · remote - your agent's requests go to mcp.xyzzylabs.ai

endpoint auth accepted our unauthenticated MCP initialize - no credentials needed to connect

license MIT - declared in the repository

npm package tc39-mcp - unscoped; check the name against the project README before installing

registry namespace io.github.xyzzylabs is GitHub-verified and matches the repo owner

03 · What Tc39 MCP can do

Prose above is summarized from the project's README and registry record - no invented capabilities.

Latest releases

v0.6.2 · 2026-08-07

Automated PATCH refresh - upstream tc39/ moved. Same code, new spec data. See spec.about for the current SHAs.

v0.6.1 · 2026-07-07

Automated PATCH refresh - upstream tc39/ moved. Same code, new spec data. See spec.about for the current SHAs.

v0.6.0 · 2026-06-29

Surfaces a clause's citations to external specs (Unicode, IETF, WHATWG) · as structured, resolvable URLs. · Added · External-spec citations on clause.get. A new optional · external_refs field on the returned Clause…

04 · Who maintains Tc39 MCP

tc39-mcp is maintained by xyzzylabs. We track 2 MCP servers from xyzzylabs - 2 actively maintained, 4 combined GitHub stars, oldest repo from May 2026. Full record: all servers from xyzzylabs.

wasm-mcp Read-only MCP server for the WebAssembly spec: instructions, types, sections, search, proposals. ★ 2

05 · Facts

repository: github.com/xyzzylabs/tc39-mcp
website: https://mcp.xyzzylabs.ai/tc39
category: other - ranked #240 of 848 actively-maintained other servers as of 2026-08-25.
release cadence: 10+ releases in the last 90 days (latest 2026-08-07)
registry: io.github.xyzzylabs/tc39-mcp (active, first published 2026-05-31 · 16 versions)
packages: npm:tc39-mcp

06 · Tc39 MCP FAQ

What is Tc39 MCP?

📖 Docs: mcp.xyzzylabs.ai/tc39 - Get started · Tools · Cookbook · Editions · Architecture · Hosting

Is Tc39 MCP still maintained?

Yes - as of 2026-08-25, its last commit was 2026-08-25 and it shipped 10+ releases in the last 90 days. We re-verify nightly.

How do I install Tc39 MCP?

Run `npx -y tc39-mcp`. The README documents one environment variable (TC39_MCP_BASE_URL) to set first. Set TC39_MCP_BASE_URL before connecting. You can also paste the ready-made client config above.

Does Tc39 MCP require authentication?

No - the endpoint accepted our unauthenticated MCP initialize when probed on 2026-08-25; you can connect without credentials.

07 · Alternatives to Tc39 MCP

Alternatives to Tc39 MCP

Maintained other servers if Tc39 MCP isn't the fit.

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