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Independent measurements of remote MCP servers. Every observation has a timestamp.

Read-only probes

MCP server · Code & DevOps

tc39-mcp

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

Checks passed
11 / 22

3 failed · 8 not measured

Median response
125 ms

Median of successful probes over 7 days

30-day uptime
Not measured

Share of countable probes over 30 days, including daily rollups. Auth challenges are excluded.

Discovered tools
17

Tool definitions returned by this server

Independent monitoring

Health & checks

Status history

Outdated check

Last connection measurement is over 24 hours old. Current availability is unknown.

Last checked
Check summary by test group
Test areaPassedFailedUnmeasured
ConnectionCan a client connect and discover tools?
410
Reliability & speedDoes it respond consistently and quickly?
004
Access & authenticationWhat is required to use this server?
102
Tool qualityAre the tool definitions usable by an agent?
220
Publisher identityCan the publisher be traced to its source?
402

Unmeasured means there is not enough evidence to decide. How these checks work

Inspect individual checks 22 recorded

Core

  • Pass
    Reachable

    Latest probe returned HTTP 200 in 125 ms.

  • Pass
    Valid handshake

    protocolVersion 2024-11-05, serverInfo.name tc39-mcp.

  • Pass
    Lists tools

    tools/list returned 17 tools.

  • Fail
    Current protocol

    Negotiated 2024-11-05. The bar is 2025-06-18 or newer.

  • Pass
    HTTPS

    The endpoint URL is https.

Performance

  • Not measured
    Fast (p50)

    Median latency 125 ms over 1 samples in 7 days. The bar is 1000 ms. Need at least 5 samples.

  • Not measured
    Consistent (p95)

    95th percentile 125 ms over 1 samples in 7 days. The bar is 3000 ms. Need at least 20 samples.

  • Not measured
    Reliable (uptime)

    1 of 1 attempts returned a tool list in 30 days (100%). The bar is 99%. Need at least 30 samples.

  • Not measured
    Stable tool list

    Fewer than two successful probes in 30 days, so tool-list stability is not measured.

Access

  • Pass
    Open access

    tools/list succeeded with no credential, and the record declares none.

  • Not measured
    Standard auth

    Auth is not required, so the OAuth metadata check does not apply.

  • Not measured
    Free tier cited

    No publisher quote has been checked.

Tools

  • Pass
    Tools described

    Every tool description is at least 20 characters.

  • Pass
    Valid input schemas

    Every inputSchema is a JSON Schema object.

  • Fail
    Parameters documented

    1 of 69 parameters have a description (1%). The bar is 80%.

  • Fail
    Safety hints

    17 tools set neither readOnlyHint nor destructiveHint.

Publisher

  • Pass
    Verified namespace

    Listed in the Official MCP Registry.

  • Not measured
    Website matches publisher

    This namespace is not a reverse domain, so the website comparison does not apply.

  • Pass
    Source repo linked

    A repository URL is on file.

  • Pass
    Repo owner matches

    The GitHub repository owner matches the namespace login.

  • Pass
    Recently updated

    Updated 2026-11-07T20:11:49.827321Z, within 180 days.

  • Not measured
    Open-source licence

    The GitHub licence lookup has not returned an OSI result yet.

Start using tc39-mcp

Connect to this server

Choose your client, copy the configuration, then enable the server in your client’s MCP settings.

Run this command in your terminal, then restart Claude Code.

Claude Code

claude mcp add --transport http tc39-mcp https://mcp.xyzzylabs.ai/tc39/mcp

Capabilities

Tools 17

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.

Discovered
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.

Discovered
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.

Discovered
proposal.get

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

Discovered
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).

Discovered
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.

Discovered
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 `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).

Discovered
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.

Discovered
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.

Discovered
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 productions (off by default).

Discovered
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).

Discovered
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.

Discovered
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.

Discovered
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.

Discovered
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.

Discovered
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.

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

Discovered

Recent measurements

Probe history

View status
Latest stored probes. Raw probe rows are kept for 14 days.
CheckedResultResponseTools
Connected125 ms17