Independent MCP server for the TC39 specs (ECMA-262 + ECMA-402): clauses, search, diffs, history.
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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.
Optional historical SHA pin (hex, 4-40 chars). Only valid when edition='main'; released editions have no per-SHA history to address.
This tool isn't marked read-only, so it may change something on the server or in an account you connected.
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.
| Argument | Type | 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. |
| id* | string | |
| spec | string | |
| edition | string |
{
"type": "object",
"required": [
"id"
],
"properties": {
"at": {
"type": "string",
"description": "Optional historical SHA pin (hex, 4-40 chars). Only valid when edition='main'; released editions have no per-SHA history to address."
},
"id": {
"type": "string"
},
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"edition": {
"type": "string"
}
}
}List parsed spec clauses with optional filters (kind, section prefix, has_algorithm). `spec` selects '262' or '402'. `at: '<sha>'` queries a historical main snapshot.
| Argument | Type | Description |
|---|---|---|
| at | string | |
| kind | string | |
| spec | string | |
| limit | number | |
| edition | string | |
| section | string | |
| has_algorithm | boolean |
{
"type": "object",
"properties": {
"at": {
"type": "string"
},
"kind": {
"type": "string"
},
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"edition": {
"type": "string"
},
"section": {
"type": "string"
},
"has_algorithm": {
"type": "boolean"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| spec | string | |
| depth | number | |
| under | string | |
| edition | string |
{
"type": "object",
"properties": {
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"depth": {
"type": "number"
},
"under": {
"type": "string"
},
"edition": {
"type": "string"
}
}
}Fetch one TC39 proposal by slug (exact) or name (case-insensitive).
| Argument | Type | Description |
|---|---|---|
| name* | string |
{
"type": "object",
"required": [
"name"
],
"properties": {
"name": {
"type": "string"
}
}
}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).
| Argument | Type | Description |
|---|---|---|
| spec | string | |
| limit | number | |
| stage | string | |
| champion | string | |
| contains | string |
{
"type": "object",
"properties": {
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"stage": {
"type": "string"
},
"champion": {
"type": "string"
},
"contains": {
"type": "string"
}
}
}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.
No arguments.
{
"type": "object",
"properties": {},
"additionalProperties": false
}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).
| Argument | Type | Description |
|---|---|---|
| id* | string | |
| spec | string | |
| limit | number | |
| edition | string | |
| direction | string | |
| include_cross_spec | boolean |
{
"type": "object",
"required": [
"id"
],
"properties": {
"id": {
"type": "string"
},
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"edition": {
"type": "string"
},
"direction": {
"enum": [
"in",
"out",
"both"
],
"type": "string"
},
"include_cross_spec": {
"type": "boolean"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| id* | string | |
| to | string | |
| from | string | |
| spec | string |
{
"type": "object",
"required": [
"id"
],
"properties": {
"id": {
"type": "string"
},
"to": {
"type": "string"
},
"from": {
"type": "string"
},
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| limit | number | |
| query* | string | |
| search_steps | boolean |
{
"type": "object",
"required": [
"query"
],
"properties": {
"limit": {
"type": "number"
},
"query": {
"type": "string"
},
"search_steps": {
"type": "boolean"
}
}
}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).
| Argument | Type | Description |
|---|---|---|
| spec | string | |
| limit | number | |
| edition | string | |
| contains | string | |
| include_sdo | boolean | |
| nonterminal | string |
{
"type": "object",
"properties": {
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"edition": {
"type": "string"
},
"contains": {
"type": "string"
},
"include_sdo": {
"type": "boolean"
},
"nonterminal": {
"type": "string"
}
}
}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).
| Argument | Type | Description |
|---|---|---|
| by | string | |
| spec | string | |
| limit | number | |
| filter | string | |
| edition | string |
{
"type": "object",
"properties": {
"by": {
"enum": [
"production",
"sdo"
],
"type": "string"
},
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"filter": {
"type": "string"
},
"edition": {
"type": "string"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| at | string | |
| spec | string | |
| limit | number | |
| query* | string | |
| edition | string | |
| search_steps | boolean |
{
"type": "object",
"required": [
"query"
],
"properties": {
"at": {
"type": "string"
},
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"query": {
"type": "string"
},
"edition": {
"type": "string"
},
"search_steps": {
"type": "boolean"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| spec | string | |
| edition | string |
{
"type": "object",
"properties": {
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"edition": {
"type": "string"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| spec | string | |
| limit | number | |
| edition | string | |
| notation* | string |
{
"type": "object",
"required": [
"notation"
],
"properties": {
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"edition": {
"type": "string"
},
"notation": {
"type": "string"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| id | string | |
| spec | string | |
| limit | number | |
| filter | string | |
| edition | string |
{
"type": "object",
"properties": {
"id": {
"type": "string"
},
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"filter": {
"type": "string"
},
"edition": {
"type": "string"
}
}
}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.
| Argument | Type | Description |
|---|---|---|
| spec | string | |
| limit | number | |
| filter | string | |
| edition | string |
{
"type": "object",
"properties": {
"spec": {
"enum": [
"262",
"402"
],
"type": "string"
},
"limit": {
"type": "number"
},
"filter": {
"type": "string"
},
"edition": {
"type": "string"
}
}
}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`.
| Argument | Type | Description |
|---|---|---|
| esid | string | |
| limit | number | |
| query | string |
{
"type": "object",
"properties": {
"esid": {
"type": "string"
},
"limit": {
"type": "number"
},
"query": {
"type": "string"
}
}
}