tc39-mcp
REMOTE · MCP.XYZZYLABS.AI · 2 COMPONENTS · SCANNED SEP 20
Independent MCP server for the TC39 specs (ECMA-262 + ECMA-402): clauses, search, diffs, history.
Available components
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 → Why this is hard to score →
Endpoint Security63
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- Authorisation not fully verified: no authorisation is required to call this server, and 17 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe. See how to fix → View diagnostics → Unverified
- HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
- The HSTS (Strict-Transport-Security) header is present. View diagnostics → Pass
- DNSSEC check failed: this domain isn't protected by DNSSEC. See how to fix → View diagnostics → Fail
Transport & Reachability100
- Verified streamable-http transport via a live MCP handshake. View diagnostics → Pass
Schema Quality & AI Usability81
- 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 Management100
- No destabilizing schema changes in the last 30 days.Pass
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
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 17 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 18 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities20
- Spec-recency check failed: implements MCP spec 2024-11-05; the latest is 2026-07-28. See how to fix → Fail
How do I install the tc39-mcp server?
tc39-mcp is a hosted endpoint at https://mcp.xyzzylabs.ai/tc39/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.
remote · mcp.xyzzylabs.ai
claude mcp add --transport http xyzzylabs-tc39-mcp 'https://mcp.xyzzylabs.ai/tc39/mcp'
{
"mcpServers": {
"xyzzylabs-tc39-mcp": {
"url": "https://mcp.xyzzylabs.ai/tc39/mcp"
}
}
} {
"servers": {
"xyzzylabs-tc39-mcp": {
"type": "http",
"url": "https://mcp.xyzzylabs.ai/tc39/mcp"
}
}
} [mcp_servers.xyzzylabs-tc39-mcp] url = "https://mcp.xyzzylabs.ai/tc39/mcp"
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"xyzzylabs-tc39-mcp": {
"type": "remote",
"url": "https://mcp.xyzzylabs.ai/tc39/mcp",
"enabled": true
}
}
} openclaw mcp add xyzzylabs-tc39-mcp --url 'https://mcp.xyzzylabs.ai/tc39/mcp' --transport streamable-http
mcp_servers:
xyzzylabs-tc39-mcp:
url: "https://mcp.xyzzylabs.ai/tc39/mcp" {
"McpServers": {
"xyzzylabs-tc39-mcp": {
"Transport": "http",
"Url": "https://mcp.xyzzylabs.ai/tc39/mcp"
}
}
} assistant mcp add xyzzylabs-tc39-mcp -t streamable-http -u 'https://mcp.xyzzylabs.ai/tc39/mcp'
{
"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.
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.
- 8 Sept 26 0
- Server version: 0.6.2 → 0.6.3 functional
- 26 Aug 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
- 25 Aug 26 0
- Stability: 0.97 → pass security
- 24 Aug 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 93 to 97. That category is still filling its 30-day observation window: 28 days of observed history at the previous scan, 29 at this one. The score rises as the window fills, whether or not the server changes.
- 11 Aug 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
- 7 Aug 26 0
- Server version: 0.6.1 → 0.6.2 functional
- 31 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
- 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
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 20 Sept 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 | 23 Aug 2026 | 21 Nov 2026 | ECDSA 256 | ECDSA-SHA256 | 35646096399f37e70e0f4daf7cc94be2 |
| 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 |
Background: What to check on a remote MCP endpoint →
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=() |
Background: How OAuth 2.1 works in the 2026 MCP spec →
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 |
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. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →
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.
| Name | Type | Req | Description |
|---|---|---|---|
| at | string | – | Optional historical SHA pin (hex, 4-40 chars). Only valid when edition='main'; released editions have no per-SHA history to address. |
| edition | string | – | – |
| id | string | yes | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| at | string | – | – |
| edition | string | – | – |
| has_algorithm | boolean | – | – |
| kind | string | – | – |
| limit | number | – | – |
| section | string | – | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| depth | number | – | – |
| edition | string | – | – |
| spec | string | – | – |
| under | string | – | – |
No output schema declared.
No examples provided.
proposal.get ~32
Fetch one TC39 proposal by slug (exact) or name (case-insensitive).
| Name | Type | Req | Description |
|---|---|---|---|
| name | string | yes | – |
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).
| Name | Type | Req | Description |
|---|---|---|---|
| champion | string | – | – |
| contains | string | – | – |
| limit | number | – | – |
| spec | string | – | – |
| stage | string | – | – |
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).
| Name | Type | Req | Description |
|---|---|---|---|
| direction | string | – | – |
| edition | string | – | – |
| id | string | yes | – |
| include_cross_spec | boolean | – | – |
| limit | number | – | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| from | string | – | – |
| id | string | yes | – |
| spec | string | – | – |
| to | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| limit | number | – | – |
| query | string | yes | – |
| search_steps | boolean | – | – |
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).
| Name | Type | Req | Description |
|---|---|---|---|
| contains | string | – | – |
| edition | string | – | – |
| include_sdo | boolean | – | – |
| limit | number | – | – |
| nonterminal | string | – | – |
| spec | string | – | – |
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).
| Name | Type | Req | Description |
|---|---|---|---|
| by | string | – | – |
| edition | string | – | – |
| filter | string | – | – |
| limit | number | – | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| at | string | – | – |
| edition | string | – | – |
| limit | number | – | – |
| query | string | yes | – |
| search_steps | boolean | – | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| edition | string | – | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| edition | string | – | – |
| limit | number | – | – |
| notation | string | yes | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| edition | string | – | – |
| filter | string | – | – |
| id | string | – | – |
| limit | number | – | – |
| spec | string | – | – |
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.
| Name | Type | Req | Description |
|---|---|---|---|
| edition | string | – | – |
| filter | string | – | – |
| limit | number | – | – |
| spec | string | – | – |
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`.
| Name | Type | Req | Description |
|---|---|---|---|
| esid | string | – | – |
| limit | number | – | – |
| query | string | – | – |
No output schema declared.
No examples provided.
What is the tc39-mcp server?
tc39-mcp is listed in the public MCP registry as io.github.xyzzylabs/tc39-mcp. Independent MCP server for the TC39 specs (ECMA-262 + ECMA-402): clauses, search, diffs, history. This page covers its hosted endpoint (https://mcp.xyzzylabs.ai/tc39/mcp).
Is the tc39-mcp server safe to use?
tc39-mcp scores 76 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.
What tools does the tc39-mcp server expose?
tc39-mcp exposes 17 tools: spec.about, clause.get, clause.list, spec.search, proposal.list, and 12 more. Their descriptions and schemas cost roughly 1,695 tokens of context every time the server is loaded.
Does the tc39-mcp server require authentication?
No. We connected to tc39-mcp without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.
Is the tc39-mcp server still maintained?
tc39-mcp is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.