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tc39-mcp

REMOTE · MCP.XYZZYLABS.AI · 2 COMPONENTS · SCANNED AUG 4

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

+5 this week 63 Trust /100
Trust breakdown (6 categories)

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. How we score →

Endpoint Security63
Transport & Reachability100
Schema Quality & AI Usability78
  • 100% of prompts and resources have a non-trivial description (not blank, and not just the item's name).Pass
  • AI-judged instruction clarity (good).Pass
  • Context-footprint check failed: tool/resource definitions use about 2309 tokens (~135/item across 17 items; 17 tools + 0 resources), over budget; trim descriptions and params. See how to fix → Fail
  • Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management30
  • Stability observed for 9 of 30 days with no destabilising changes; credit accrues until the full window elapses.Partial
Tool Coverage67
  • 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
  • 1% of tool parameters carry a description.Partial
Capabilities20
  • Spec-recency check failed: implements MCP spec 2024-11-05; the latest is 2026-07-28. See how to fix → Fail
Install

Add this component to your MCP client. Where a client-specific snippet is available, pick your client below and copy it straight into your config; otherwise use the connection detail shown.

remote · mcp.xyzzylabs.ai

# add to Claude Code
claude mcp add --transport http xyzzylabs-tc39-mcp https://mcp.xyzzylabs.ai/tc39/mcp
# ~/.codex/config.toml
[mcp_servers.xyzzylabs-tc39-mcp]
url = "https://mcp.xyzzylabs.ai/tc39/mcp"
// opencode.json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "xyzzylabs-tc39-mcp": {
      "type": "remote",
      "url": "https://mcp.xyzzylabs.ai/tc39/mcp",
      "enabled": true
    }
  }
}
# add to OpenClaw
openclaw mcp add xyzzylabs-tc39-mcp --url https://mcp.xyzzylabs.ai/tc39/mcp --transport streamable-http
# ~/.hermes/config.yaml
mcp_servers:
  xyzzylabs-tc39-mcp:
    url: "https://mcp.xyzzylabs.ai/tc39/mcp"
// mcp.json
{
  "mcpServers": {
    "xyzzylabs-tc39-mcp": {
      "type": "http",
      "url": "https://mcp.xyzzylabs.ai/tc39/mcp"
    }
  }
}

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

Changelog

Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.

  • 3 Aug 26 +1

    No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

  • 1 Aug 26 +1

    No change was recorded against any check on this day. Stability & Change Management went from 17 to 20. That category is still filling its 30-day observation window: 5 days of observed history at the previous scan, 6 at this one. The score rises as the window fills, whether or not the server changes.

  • 31 Jul 26 +2
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 30 Jul 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 29 Jul 26 +1

    No change was recorded against any check on this day. Stability & Change Management went from 7 to 10. That category is still filling its 30-day observation window: 2 days of observed history at the previous scan, 3 at this one. The score rises as the window fills, whether or not the server changes.

  • 28 Jul 26 +1

    No change was recorded against any check on this day. Stability & Change Management went from 3 to 7. That category is still filling its 30-day observation window: 1 days of observed history at the previous scan, 2 at this one. The score rises as the window fills, whether or not the server changes.

  • 27 Jul 26 0
    • We updated how we score, so this day's move reflects our rubric, not a change to the server See what changed → functional
  • 26 Jul 26 57

    First indexed and scored.

Diagnostics

Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.

Captured 4 Aug 2026 · Probed https://mcp.xyzzylabs.ai/tc39/mcp

TLS valid

Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .

Subject Issuer Valid from Valid until Key Signature Serial
CN=xyzzylabs.ai CN=WE1,O=Google Trust Services,C=US 25 Jun 2026 23 Sept 2026 ECDSA 256 ECDSA-SHA256 ce718b122407157d0ec5b049e6ebd6d9
SANs: xyzzylabs.ai, mcp.xyzzylabs.ai, *.mcp.xyzzylabs.ai
CN=WE1,O=Google Trust Services,C=US (CA) CN=GTS Root R4,O=Google Trust Services LLC,C=US 13 Dec 2023 20 Feb 2029 ECDSA 256 ECDSA-SHA384 7ff31977972c224a76155d13b6d685e3
CN=GTS Root R4,O=Google Trust Services LLC,C=US (CA) CN=GlobalSign Root CA,OU=Root CA,O=GlobalSign nv-sa,C=BE 15 Nov 2023 28 Jan 2028 ECDSA 384 SHA256-RSA 7fe530bf331343bedd821610493d8a1b
DNSSEC insecure

Validation of mcp.xyzzylabs.ai. Not signed

Zone DS Keys Algorithms Outcome
. trust_anchor 20326, 38696 8, 8 Verified
ai. present 3799 8 Verified
xyzzylabs.ai. absent Unsigned (proven) parent-signed NSEC/NSEC3 proves an unsigned delegation
Authentication No authorisation required

The endpoint answered without asking for a token. Anyone who knows the URL can reach it.

Result No authorisation required
HTTP status 200
Header Value
strict-transport-security max-age=31536000
x-content-type-options nosniff
x-frame-options DENY
referrer-policy strict-origin-when-cross-origin
permissions-policy camera=(), microphone=(), geolocation=(), browsing-topics=()
Transports 2 probes
Transport URL Outcome Status Location
streamable-http https://mcp.xyzzylabs.ai/tc39/mcp Verified 200
http (plaintext) http://mcp.xyzzylabs.ai/tc39/mcp HTTPS enforced 308 https://mcp.xyzzylabs.ai/tc39/mcp
MCP tools — 17 exposed · ~1,695 tokens

The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability.

Tool Tokens
clause.get ~126

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.

NameTypeReqDescription
atstringOptional historical SHA pin (hex, 4-40 chars). Only valid when edition='main'; released editions have no per-SHA history to address.
editionstring
idstringyes
specstring

No output schema declared.

No examples provided.

clause.list ~98

List parsed spec clauses with optional filters (kind, section prefix, has_algorithm). `spec` selects '262' or '402'. `at: '<sha>'` queries a historical main snapshot.

NameTypeReqDescription
atstring
editionstring
has_algorithmboolean
kindstring
limitnumber
sectionstring
specstring

No output schema declared.

No examples provided.

clause.outline ~84

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.

NameTypeReqDescription
depthnumber
editionstring
specstring
understring

No output schema declared.

No examples provided.

proposal.get ~32

Fetch one TC39 proposal by slug (exact) or name (case-insensitive).

NameTypeReqDescription
namestringyes

No output schema declared.

No examples provided.

proposal.list ~105

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).

NameTypeReqDescription
championstring
containsstring
limitnumber
specstring
stagestring

No output schema declared.

No examples provided.

spec.about ~57

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.

Input schema present but exposes no named parameters.

No output schema declared.

No examples provided.

spec.crossrefs ~179

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 `external` category: the clause's citations to external specs (Unicode, IETF, WHATWG) as resolvable URLs. Set `include_cross_spec: true` to also resolve outgoing references from ECMA-262 → ECMA-402 (or vice versa).

NameTypeReqDescription
directionstring
editionstring
idstringyes
include_cross_specboolean
limitnumber
specstring

No output schema declared.

No examples provided.

spec.diff ~97

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.

NameTypeReqDescription
fromstring
idstringyes
specstring
tostring

No output schema declared.

No examples provided.

spec.global_search ~88

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.

NameTypeReqDescription
limitnumber
querystringyes
search_stepsboolean

No output schema declared.

No examples provided.

spec.grammar ~124

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 productions (off by default).

NameTypeReqDescription
containsstring
editionstring
include_sdoboolean
limitnumber
nonterminalstring
specstring

No output schema declared.

No examples provided.

spec.sdo_index ~107

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).

NameTypeReqDescription
bystring
editionstring
filterstring
limitnumber
specstring

No output schema declared.

No examples provided.

spec.search ~91

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.

NameTypeReqDescription
atstring
editionstring
limitnumber
querystringyes
search_stepsboolean
specstring

No output schema declared.

No examples provided.

spec.snapshots ~96

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.

NameTypeReqDescription
editionstring
specstring

No output schema declared.

No examples provided.

spec.symbol_resolve ~91

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.

NameTypeReqDescription
editionstring
limitnumber
notationstringyes
specstring

No output schema declared.

No examples provided.

spec.tables ~86

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.

NameTypeReqDescription
editionstring
filterstring
idstring
limitnumber
specstring

No output schema declared.

No examples provided.

spec.well_known_intrinsics ~106

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.

NameTypeReqDescription
editionstring
filterstring
limitnumber
specstring

No output schema declared.

No examples provided.

test262.search ~128

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, flags), capped at `limit` (default 20). Supply at least one of `query` / `esid`.

NameTypeReqDescription
esidstring
limitnumber
querystring

No output schema declared.

No examples provided.