How do I install the tc39 specs (ecma mcp server?

Use a recorded configuration for your client, replace example credential values and paths, and verify the documented runtime. Restart or reconnect the client, then inspect the available tools.

What credentials does it need?

It reads `TC39_MCP_BASE_URL` from the environment. Store these in your client's env block or a secrets manager — never commit them to a repository — and grant the narrowest scope that still covers your use case.

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TC39 Specs (ECMA MCP Server

Parsed ECMA-262 and ECMA-402 specs over MCP — clauses, algorithm steps, cross-references, edition diffs, test262 and proposal search.

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What is the TC39 Specs (ECMA MCP Server?

Parsed ECMA-262 and ECMA-402 specs over MCP — clauses, algorithm steps, cross-references, edition diffs, test262 and proposal search.

What you get

Snapshots resolve through a local cache → hosted Worker → bundled fallback chain. The stdio transport (npx tc39-mcp) fetches each snapshot from the hosted Cloudflare Worker on a cold cache, writes it under ~/.cache/tc39-mcp/, and serves it from disk thereafter — revalidating only when the local copy is older than ~4 hours (a conditional If-None-Match request). The npm package also bundles the latest stable + main editions of both specs plus the test262 and proposals indexes; when the Worker is unreachable, those are served straight from the package (the offline fallback — not written to the cache). The

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Compare MCP servers by category, or browse hosted MCP servers if you prefer an endpoint over a local process.

Maintainer setup documentation.

Recorded tools

Check the linked publisher documentation and your connected client's tool list. Names and availability can vary with the server version and account permissions.

Tool	What it does
Goal	Tool(s)

How to install the TC39 Specs (ECMA MCP Server

{
  "mcpServers": {
    "tc39": {
      "command": "npx",
      "args": [
        "tc39-mcp"
      ]
    }
  }
}

From the project documentation. Replace placeholders and example paths before connecting.

Example prompts to try

“Use TC39 Specs (ECMA to Goal.”

Frequently asked questions

Parsed ECMA-262 and ECMA-402 specs over MCP — clauses, algorithm steps, cross-references, edition diffs, test262 and proposal search. Confirm the tools offered by your installed version in the connected client. Tool availability and permissions depend on the server and account configuration.