tc39-mcp

Gives Claude and other MCP clients structured JSON access to the ECMA-262 and ECMA-402 specs instead of forcing them to parse megabytes of HTML. You get 19 tools spanning clause lookup, cross-reference traversal (both directions, including 262↔402 hops), edition diffs back to ES2016, git history via pickaxe, test262 search by esid, and proposal tracking. Ships offline-first via stdio so every query hits local snapshots with zero network calls, or use the hosted Cloudflare Worker for shared HTTP access. Every response is SHA-pinned to a specific upstream commit. Reach for this when you need an agent to reason about spec semantics, track prose changes across releases, or verify test coverage without hallucinating step numbers.