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wasm-mcp

by xyzzylabs · remote · local (npm) · no sign-in to list tools · v0.2.16 · published by GitHub user xyzzylabs

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

Changes · 2
CompareRegistry entry

9 tools: 2 change things and 7 only read.

Scanned Oct 21, 2026

2 checks matched something in the tool definitions. No finding is not a safety guarantee. How the checks work.

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

Findings

Matches of fixed checks, with the text they matched.

2 warn
  • Warntype_get

    The server marks "type_get" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true}; The name "type_get" says "type": a word for a change.

    What this check looks for
  • Warnsection_list

    The server marks "section_list" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true}; The name "section_list" says "list": a word for reading.

    What this check looks for

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

9 tools

Changes things 2Claude Code: ask
  • section_listNavigate the clause tree of a spec (`core` / `js-api` / `web-api`), filterable by source `path` (`syntax`, `valid`, `exec`, `binary`, `text`, `appendix`), `anchor_prefix`, `titled_…1 finding

    Why it is in this group

    • The name "section_list" says "list": a word for reading.
    • The description's first verb is "navigate": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "section_list" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true}; The name "section_list" says "list": a word for reading.

      What this check looks for
    Description, as the server wrote it
    Navigate the clause tree of a spec (`core` / `js-api` / `web-api`), filterable by source `path` (`syntax`, `valid`, `exec`, `binary`, `text`, `appendix`), `anchor_prefix`, `titled_only`, and `max_level`.

    Annotations the server declares

    • readOnlyHint: true
  • type_getLook up a value type (`i32`, `funcref`, `v128`, …) or type form (`functype`, `limits`, `memtype`, …): classification, sibling members, defining clause prose, formal refs, and URL.1 finding

    Why it is in this group

    • The name "type_get" says "type": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "type_get" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true}; The name "type_get" says "type": a word for a change.

      What this check looks for
    Description, as the server wrote it
    Look up a value type (`i32`, `funcref`, `v128`, …) or type form (`functype`, `limits`, `memtype`, …): classification, sibling members, defining clause prose, formal refs, and URL.

    Annotations the server declares

    • readOnlyHint: true
Only reads 7Claude Code: allow
  • instruction_getFetch one WebAssembly instruction by mnemonic (`i32.add`) or binary opcode (`0x6a`, multi-byte `0xfd 0x89 0x02`): opcode bytes, category, introducing version, stack type signature,…No findings

    Why it is in this group

    • The name "instruction_get" says "get": a word for reading.
    Description, as the server wrote it
    Fetch one WebAssembly instruction by mnemonic (`i32.add`) or binary opcode (`0x6a`, multi-byte `0xfd 0x89 0x02`): opcode bytes, category, introducing version, stack type signature, validation/execution anchors + URLs, and `traps` (runtime trap conditions with canonical names; empty + `can_trap:false` when it never traps).

    Annotations the server declares

    • readOnlyHint: true
  • instruction_listEnumerate WebAssembly instructions, filterable by `category`, `introduced_in` (1.0|2.0|3.0), mnemonic `prefix`, and `can_trap` (only trapping / only non-trapping).No findings

    Why it is in this group

    • The name "instruction_list" says "list": a word for reading.
    Description, as the server wrote it
    Enumerate WebAssembly instructions, filterable by `category`, `introduced_in` (1.0|2.0|3.0), mnemonic `prefix`, and `can_trap` (only trapping / only non-trapping). Rows (incl. `can_trap`) sorted by opcode.

    Annotations the server declares

    • readOnlyHint: true
  • proposal_listList WebAssembly proposals + phases.No findings

    Why it is in this group

    • The name "proposal_list" says "list": a word for reading.
    Description, as the server wrote it
    List WebAssembly proposals + phases. Filter by `status` (phase-0…phase-5, finished, inactive), `phase` (0–5), `champion`, `affects` (core|js-api|web-api), or `contains`.

    Annotations the server declares

    • readOnlyHint: true
  • section_getFetch one spec clause by id or anchor across `core` / `js-api` / `web-api` (`syntax-numtype`, `valid-unreachable`, `modules`, `streaming-modules`, …): title, prose, cross-reference…No findings

    Why it is in this group

    • The name "section_get" says "get": a word for reading.
    Description, as the server wrote it
    Fetch one spec clause by id or anchor across `core` / `js-api` / `web-api` (`syntax-numtype`, `valid-unreachable`, `modules`, `streaming-modules`, …): title, prose, cross-references, SpecTec formal refs, and rendered URL.

    Annotations the server declares

    • readOnlyHint: true
  • spec_versionReturn this server's package version plus the pinned upstream commit SHA(s) the bundled data was indexed from.No findings

    Why it is in this group

    • The description's first verb is "return": a word for reading.
    Description, as the server wrote it
    Return this server's package version plus the pinned upstream commit SHA(s) the bundled data was indexed from.

    Annotations the server declares

    • readOnlyHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 0.2.16. Values in angle brackets are yours to fill in.

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

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__wasm__spec_version",
      "mcp__wasm__instruction_get",
      "mcp__wasm__instruction_list",
      "mcp__wasm__instruction_search",
      "mcp__wasm__section_get",
      "mcp__wasm__spec_search",
      "mcp__wasm__proposal_list"
    ],
    "ask": [
      "mcp__wasm__type_get",
      "mcp__wasm__section_list"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as wasm. Review it before you use it.