# wasm-mcp (npm · wasm-mcp)

Read-only MCP server for the WebAssembly spec: instructions, types, sections, search, proposals.

- Trust score: 72/100 (medium)
- Change this week: +30
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-08-03

## Components

- remote · `mcp.xyzzylabs.ai`: 64/100, [markdown](https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp.md), [page](https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp)
- npm · `wasm-mcp`: 72/100 (this document), [markdown](https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp-2.md), [page](https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp-2)

## Channel facts

- Registry: `npm`
- Package: `wasm-mcp`
- Version: `0.2.16`
- Transport: `stdio`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically from public evidence about the published package, including repeated runs of it in an isolated sandbox, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-08-03.

- **Supply Chain Security**: 86/100
  - No malware found by supply-chain analysis.
  - Only part of the dependency tree could be resolved (94 of 98), so this covers what we could see, not the whole tree.
  - No install/post-install scripts declared.
  - Only part of the dependency tree could be resolved (94 of 98), so this covers what we could see, not the whole tree.
- **Provenance & Transparency**: 97/100
  - Source repository is publicly reachable at the declared URL.
  - Cryptographically verified build provenance (signed, bound to xyzzylabs/wasm-mcp).
  - Clear OSI-approved license (MIT).
  - Actively maintained (last published 22 days ago).
  - Disclosure check failed: no security disclosure policy was found in the source repository.
- **Schema Quality & AI Usability**: 59/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 2807 tokens (~311/item across 9 items; 9 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 0/100
  - Stability not yet verified: not enough scan history yet (needs a 30-day window).
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
- **Capabilities**: 100/100
  - Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.

**Unverified: 1 category.** A category scored 0 because we could not verify it: a data source with nothing on this package, evidence we could not reach, or a check we could not run. We only credit what we can confirm.

## Install

### Claude

```bash
claude mcp add xyzzylabs-wasm-mcp -- npx -y wasm-mcp
```

### Codex

```bash
codex mcp add xyzzylabs-wasm-mcp -- npx -y wasm-mcp
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "xyzzylabs-wasm-mcp": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "wasm-mcp"
      ],
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add xyzzylabs-wasm-mcp --command npx --arg -y --arg wasm-mcp
```

### Hermes

```yaml
mcp_servers:
  xyzzylabs-wasm-mcp:
    command: "npx"
    args: ["-y", "wasm-mcp"]
```

### Other

```json
{
  "mcpServers": {
    "xyzzylabs-wasm-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "wasm-mcp"
      ]
    }
  }
}
```

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-08-02 (score 72, +55)

- [security improvement] Install scripts: unverified → pass
- [security improvement] Provenance: unverified → pass
- [security improvement] Known CVEs: unverified → partial
- [security improvement] Malware scan: unverified → pass
- [security] Stability: Stability not yet verified: not enough scan history yet (needs a 30-day window).
- [security] The attested source repository moved: xyzzylabs/wasm-mcp
- [functional improvement] License: unverified → pass
- [functional improvement] Maintenance: unverified → pass
- [functional improvement] Schema quality: unverified → excellent
- [functional improvement] Dependency health: unverified → partial
- [functional improvement] MCP protocol: unverified → pass
- [functional] Licence: MIT

### 2026-08-01 (score 17, +12)

- [functional improvement] Tool coverage: unverified → 100

### 2026-07-31 (score 5, −37)

- [functional] We updated how we score, so this day's move reflects our rubric, not a change to the server

### 2026-07-30 (score 42, +18)

- [functional improvement] Tool coverage: unverified → 100

### 2026-07-28 (score 24, −18)

- [functional regression] Tool coverage: 100 → unverified
- [functional] First check of Schema quality: unverified

### 2026-07-27 (score 42)

First indexed and scored.

## MCP tools (9)

### `spec_version` (~55 tokens)

Pinned spec version

Return self-description of this MCP server: package name + version, plus the pinned upstream commit SHA for every spec snapshot baked into the package. Use this first when citing the spec, or to verify the server's freshness and reproducibility.

### `instruction_get` (~246 tokens)

Get instruction

Fetch one WebAssembly instruction by mnemonic (`i32.add`, `br_if`) or binary opcode (`0x6a`, `0xfd 0x89 0x02`) as structured JSON: opcode bytes, category, introducing version, stack type signature, validation/execution prose anchors + spec URLs, and `traps` — the runtime conditions under which it traps (each with the spec's canonical trap name; empty + `can_trap: false` for instructions that never trap). Provide `mnemonic` or `opcode` (mnemonic wins if both match).

Input parameters:

- `mnemonic` (string): Instruction mnemonic, e.g. `i32.add`, `br_if`, `local.get`. Case-insensitive. Exact match.
- `opcode` (string): Binary opcode as hex bytes, e.g. `0x6a`, `6a`, or multi-byte `0xfd 0x89 0x02`. Exact match. Used when `mnemonic` is absent or doesn't match.
- `version` (string): WebAssembly spec version to query. `latest` (default) is the current served version; `main` is the upstream working draft.

### `instruction_list` (~311 tokens)

List instructions

Enumerate WebAssembly instructions with optional filters: `category` (control, numeric, parametric, variable, table, memory, ref, i31, struct, array, extern, vec), `introduced_in` (1.0 | 2.0 | 3.0), `prefix` (mnemonic prefix like `i32.`), and `can_trap` (only trapping / only non-trapping instructions). Returns lightweight rows (incl. `can_trap`) sorted by opcode; follow up with instruction_get for full detail incl. trap conditions.

Input parameters:

- `can_trap` (boolean): Filter by trapping behavior: `true` keeps only instructions that can trap at runtime, `false` keeps only those that never trap. See instruction_get for the per-instruction trap conditions.
- `category` (string): Filter by instruction category: control, numeric, parametric, variable, table, memory, ref, i31, struct, array, extern, vec (vector/SIMD).
- `introduced_in` (string): Filter to instructions introduced in this WebAssembly version: `1.0`, `2.0`, or `3.0`.
- `prefix` (string): Filter to mnemonics starting with this prefix, e.g. `i32.` or `v128.`. Case-insensitive.
- `version` (string): WebAssembly spec version to query. `latest` (default) is the current served version; `main` is the upstream working draft.

### `instruction_search` (~150 tokens)

Search instructions

Search WebAssembly instructions by free-text query, matched against mnemonic (exact > substring), category name, and opcode hex. The entry point when you don't know the exact mnemonic. Returns ranked lightweight hits with a `matched_on` field; follow up with instruction_get.

Input parameters:

- `limit` (integer): Max ranked hits returned.
- `query` (string, required): Search text. Matched against mnemonic (exact > substring), category name, and opcode hex. E.g. `extend`, `trunc`, `vec`, `0x6a`.
- `version` (string): WebAssembly spec version to query. `latest` (default) is the current served version; `main` is the upstream working draft.

### `type_get` (~248 tokens)

Get type

Look up a WebAssembly type or type form by name: concrete value types (`i32`, `i64`, `f32`, `f64`, `v128`, `funcref`, `externref`, …) or type forms (`functype`, `limits`, `memtype`, `tabletype`, `globaltype`, `reftype`, `valtype`, `rectype`, `heaptype`, …). Returns its classification, sibling members for category types, defining clause prose, SpecTec formal-rule references, and the rendered spec URL.

Input parameters:

- `name` (string, required): Type or type-form name. Concrete value types: `i32`, `i64`, `f32`, `f64`, `v128`, `funcref`, `externref`, … Type forms: `functype`, `limits`, `memtype`, `tabletype`, `globaltype`, `reftype`, `valtype…
- `version` (string): WebAssembly spec version to query. `latest` (default) is the current served version; `main` is the upstream working draft.

### `section_get` (~286 tokens)

Get spec section

Fetch one spec clause by id or anchor, across `core` / `js-api` / `web-api` (set `spec`). For core: `syntax-numtype`, `valid-unreachable`, `binary-instr`, … For the embedding specs: `modules`, `memories`, `streaming-modules`, … Matches the rendered spec's stable fragment ids. Returns the clause title, cleaned prose, cross-references, the SpecTec `formal_refs` it cites (core), and the rendered URL. Core validation/execution clauses are SpecTec-generated: prose may be terse, but formal_refs + url point to the formal rule.

Input parameters:

- `id` (string, required): Clause id or anchor. For `core`: `syntax-numtype`, `valid-unreachable`, `binary-instr`, … For `js-api` / `web-api`: `modules`, `memories`, `streaming-modules`, … These match the stable fragment ids i…
- `spec` (string): Which WebAssembly spec to query: `core` (default; instructions, types, validation, execution, formats), `js-api` (JavaScript embedding), or `web-api` (Web platform integration).
- `version` (string): WebAssembly spec version to query. `latest` (default) is the current served version; `main` is the upstream working draft.

### `section_list` (~330 tokens)

List spec sections

Enumerate spec clauses for navigation, across `core` / `js-api` / `web-api` (set `spec`). Filter by source `path` (core: `intro`, `syntax`, `valid`, `exec`, `binary`, `text`, `appendix`, or sub-paths like `syntax/types`), `anchor_prefix`, `titled_only`, and `max_level`. Returns lightweight rows {id, anchors, title, level, path, url}; follow up with section_get.

Input parameters:

- `anchor_prefix` (string): Filter to clauses whose id/anchor starts with this prefix, e.g. `syntax-`, `valid-`, `exec-`.
- `max_level` (integer): Cap heading depth (1 = page titles only). Anchor-only blocks are unaffected.
- `path` (string): Filter to a source path / prefix. Top-level areas: `intro`, `syntax` (structure), `valid` (validation), `exec` (execution), `binary`, `text`, `appendix`. Sub-paths like `syntax/types` also work.
- `spec` (string): Which WebAssembly spec to query: `core` (default; instructions, types, validation, execution, formats), `js-api` (JavaScript embedding), or `web-api` (Web platform integration).
- `titled_only` (boolean): Drop anchor-only content blocks (keep only clauses with a heading).
- `version` (string): WebAssembly spec version to query. `latest` (default) is the current served version; `main` is the upstream working draft.

### `spec_search` (~227 tokens)

Search spec

Full-text search across the section index of a spec (`core` / `js-api` / `web-api`, set `spec`) — clause anchors/ids, titles, and prose. The entry point when you don't know the exact anchor. Returns ranked hits with a `matched_on` field (anchor-exact > title > anchor > prose) and a prose snippet for body matches; follow up with section_get.

Input parameters:

- `limit` (integer): Max ranked hits returned.
- `query` (string, required): Search text. Matched against clause anchors/ids, titles, and prose. E.g. `block type`, `trap`, `funcref`, `streaming compilation`.
- `spec` (string): Which WebAssembly spec to query: `core` (default; instructions, types, validation, execution, formats), `js-api` (JavaScript embedding), or `web-api` (Web platform integration).
- `version` (string): WebAssembly spec version to query. `latest` (default) is the current served version; `main` is the upstream working draft.

### `proposal_list` (~217 tokens)

List WebAssembly proposals

List WebAssembly proposals and their phases from the pinned WebAssembly/proposals repository. Filter by `status` (phase-0…phase-5, finished, inactive), `phase` (0–5), `champion` substring, `affects` (finished proposals touching core / js-api / web-api), or `contains` (name/champion substring). Each row carries name, status, phase, champion, affected_specs, spec_version, and the proposal URL.

Input parameters:

- `affects` (string): Filter to finished proposals affecting a given spec: `core`, `js-api`, or `web-api`.
- `champion` (string): Champion substring, case-insensitive.
- `contains` (string): Name or champion substring, case-insensitive.
- `phase` (integer): Filter by numeric phase 0–5 (active + finished proposals carry a phase).
- `status` (string): Filter by lifecycle status: `phase-0`…`phase-5`, `finished` (merged into the spec), or `inactive`.

## Diagnostics

Captured diagnostic sections: Provenance, Dependencies. The full working is on the page: https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp-2#diagnostics

## Score history

- 2026-08-03: 72
- 2026-08-02: 72
- 2026-08-01: 17
- 2026-07-31: 5
- 2026-07-30: 42
- 2026-07-28: 24
- 2026-07-27: 42

## Links

- npm package: https://www.npmjs.com/package/wasm-mcp
- Socket report: https://socket.dev/npm/package/wasm-mcp
- Repository: https://github.com/xyzzylabs/wasm-mcp
- Website: https://mcp.xyzzylabs.ai/wasm/
- Changelog RSS feed: https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp-2/changelog.xml
- Changelog JSON feed: https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp-2/changelog.json
- HTML version of this page: https://verifymcp.io/servers/xyzzylabs-wasm-mcp/wasm-mcp-2