MCP for the TC39 specs (not affiliated with Ecma/TC39). SHA-pinned ECMA-262 + ECMA-402, AOID-aware search, cross-spec references, edition diffs, git history — read-only, deterministic, hosted-safe.
Latest release v0.6.3 · 8 Sept 2026
3 files for GitHub Copilot, Codex, OpenCode and Claude Code: tc39-mcp copilot-instructions.md, tc39-mcp AGENTS.md, tc39-mcp CLAUDE.md — 1,590 tokens loaded in every session.
.github/copilot-instructions.md A 747 tok AGENTS.md A 838 tok CLAUDE.md A 5 tok These files are xyzzylabs/tc39-mcp's own configuration — they tell GitHub Copilot, Codex, OpenCode and Claude Code how to work on this repository, so they are not mods to install elsewhere. Copy one as a starting point and replace the parts that are about this project.