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tc39-mcp

io.github.xyzzylabs/tc39-mcp · v0.6.4

Independent MCP server for the TC39 specs (ECMA-262 + ECMA-402): clauses, search, diffs, history.

MCPremotelocal · npmno credentials

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Last check

Reachable, 17 tools, protocol 2024-11-05 · checked 2026-10-17

Test & rating

B 74/100

What it does: 17 tools · 0 read, 0 write

No tool could be tested safely. Only read-only tools that need no input are called.

How the rating is made
  • Answers without login: +30
  • Speed of first answer: +10
  • Lists tools: +10
  • Tool descriptions: +15
  • Parameter descriptions: +1
  • Read/write annotations: 0
  • Safe test call: +8
  • More than 80 tools: 0

Tested 2026-10-17. Fixed rules, no AI model. Grade A needs a successful real call.

Install

Remote URL
https://mcp.xyzzylabs.ai/tc39/mcp
Package
registry:   npm
identifier: tc39-mcp
version:    0.6.4
transport:  stdio

Tools

17 tools listed at last check
  • spec.about Self-description of this MCP server: package name + version, per-snapshot pin metadata (sha, fetched_at, biblio_commit, clause_count) for every supported (spec, edition), plus test262 + proposals index headers when present.
  • clause.get Fetch a parsed TC39 clause as structured JSON. `spec` selects '262' (default) or '402'. `edition` defaults to 'latest'. `at: '<sha>'` pins to a historical main snapshot (only valid for edition='main'); omit to query the live snapshot.
  • clause.list List parsed spec clauses with optional filters (kind, section prefix, has_algorithm). `spec` selects '262' or '402'. `at: '<sha>'` queries a historical main snapshot.
  • spec.search Search the parsed spec by clause id / aoid / title (+ step text with `search_steps`). Aoid-exact ranks first. `at: '<sha>'` searches a historical main snapshot.
  • proposal.list List TC39 proposals from the static index (tc39/proposals). Filter by spec ('262'|'402'), stage ('0'|'1'|'2'|'2.7'|'3'|'finished'|'inactive'|'active'), champion (substring), or contains (name/slug substring).
  • proposal.get Fetch one TC39 proposal by slug (exact) or name (case-insensitive).
  • spec.grammar Query grammar productions captured from the spec's `<emu-grammar>` blocks. `{ nonterminal }` returns every production for that non-terminal (exact match); `{ contains }` filters by RHS / name substring; neither lists all non-terminals + their production counts. `include_sdo` folds in SDO-attached pr
  • spec.tables List or fetch parsed `<emu-table>` content. `{ id }` returns exactly that table (full columns + rows); otherwise list table summaries, optionally narrowed by a `filter` substring over the caption or id.
  • spec.sdo_index Index Syntax-Directed Operations by the grammar production they're defined on. `by: 'production'` (default) groups SDOs under each production; `by: 'sdo'` groups productions under each SDO title. `filter` narrows to keys containing a substring (case-insensitive).
  • clause.outline Return the section tree (table of contents) for a parsed (spec, edition). `depth` caps how deep the tree descends (1 = top-level only); `under` limits the tree to descendants of one clause id.
  • spec.global_search Run spec.search across both ECMA-262 and ECMA-402 in one call and interleave hits by score. Each hit is tagged with the spec it came from. Use it when you don't know which spec defines a symbol. `search_steps` also matches algorithm step text.
  • spec.snapshots List the live (spec, edition, sha, fetched_at) snapshots the hosted Worker is serving from R2. Filter by `spec` ('262'|'402') or `edition` (e.g. 'main', 'es2026'). Historical SHA-pinned copies are reachable via `at:` on clause.get / spec.search but aren't enumerated here.
  • spec.symbol_resolve Resolve spec notation like `[[Prototype]]` (internal slot), `%Object.prototype%` (well-known intrinsic), or `~number~` (sigil enum): return clauses that mention or define it, ranked by occurrence with a bump for definition-y sections.
  • spec.well_known_intrinsics Enumerate the well-known intrinsics in a spec with their probable defining clauses. Driven from the canonical §6.1.7.4 WKI table when present (ECMA-262), else a `%X%` prose scan (e.g. ECMA-402). `filter` narrows by bare-name substring.
  • spec.diff Clause-level diff of one clause across two editions of a spec. Reports identical / modified / added / removed plus a field-level breakdown (title, signature, step count, reworded step indices, notes, crossrefs). `from` defaults to the latest stable release, `to` to main.
  • spec.crossrefs For a clause id, return its outgoing references (clauses it cites) and/or incoming references (clauses that cite it — the back-reference index the parse alone doesn't expose). The reverse index is AOID-densified from step text. `direction`: 'in' | 'out' | 'both' (default). Outgoing also carries an `
  • test262.search Search the tc39/test262 conformance suite from its indexed front-matter. `query` AND-matches whitespace tokens (case-insensitive) across each test's description + path; `esid` prefix-matches the front-matter esid. Returns ranked hits (path, GitHub url at the indexed SHA, esid, description, features,

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