wasm-mcp

xyzzylabs/wasm-mcp

Gives Claude read-only access to the WebAssembly core specification, pinned to a specific commit for deterministic results. Query individual instructions by mnemonic or opcode to get stack signatures, validation rules, and trap conditions. Search the spec with free text, navigate section trees across core/js-api/web-api, and list WebAssembly proposals by phase or champion. All spec data is baked in at build time, so there's no runtime network or code execution. Useful when you're writing or debugging Wasm tooling, need to verify instruction semantics, or want Claude to reference formal validation rules without hallucinating. Available as a local stdio server via npx or a public unauthenticated HTTP endpoint with per-IP rate limiting.

GitHub stars: 2
tools: 9
transport: STDIO, HTTP
last updated: Jul 11, 2026

View on GitHub

Install

From registry metadata

$ npx add-mcp https://mcp.xyzzylabs.ai/wasm/mcp --name wasm-mcp

Run in your terminal. add-mcp asks which agents to add it to (Claude Code, Codex, Cursor and more). Add -g to install it for every project.

Review the command, arguments and environment values before installing. MCP servers run with your local permissions.

Other ways

Claude Code

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

Run in your terminal. Add --scope user to make it available in every project.

Tools

Verified live · 9 tools

Verified live against the running server on Nov 6, 2026.

spec_versionReturn this server's package version plus the pinned upstream commit SHA(s) the bundled data was indexed from.

Return this server's package version plus the pinned upstream commit SHA(s) the bundled data was indexed from.

No parameters. Call it with no arguments.

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, validation/execution anchors + URLs, and `traps` (runtime trap conditions with canonical names;...2 params

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;...

Parameters* required

mnemonicstring

Instruction mnemonic, e.g. `i32.add`. Case-insensitive, exact.

opcodestring

Binary opcode hex, e.g. `0x6a` or `0xfd 0x89 0x02`. Exact.

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). Rows (incl. `can_trap`) sorted by opcode.4 params

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.

Parameters* required

can_trapboolean

Keep only instructions that can (true) / cannot (false) trap.

categorystring

Instruction category.one of control · numeric · parametric · variable · table · memory

introduced_instring

Introducing version.one of 1.0 · 2.0 · 3.0

prefixstring

Mnemonic prefix, e.g. `i32.`. Case-insensitive.

instruction_searchRanked free-text search across instruction mnemonics, categories, and opcode hex. Returns hits with a `matched_on` field.2 params

Ranked free-text search across instruction mnemonics, categories, and opcode hex. Returns hits with a `matched_on` field.

Parameters* required

limitinteger

Max hits.

query*string

Search text.

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 params

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

Parameters* required

name*string

Type or type-form name. Case-insensitive, exact.

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-references, SpecTec formal refs, and rendered URL.2 params

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.

Parameters* required

id*string

Clause id or anchor.

specstring

Which spec (default core).one of core · js-api · web-api

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_only`, and `max_level`.5 params

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`.

Parameters* required

anchor_prefixstring

Id/anchor prefix.

max_levelinteger

Cap heading depth.

pathstring

Source path / prefix.

specstring

Which spec (default core).one of core · js-api · web-api

titled_onlyboolean

Drop anchor-only blocks.

spec_searchFull-text search across clause anchors, titles, and prose of a spec (`core` / `js-api` / `web-api`). Ranked anchor-exact > title > anchor > prose, with snippets for body matches.3 params

Full-text search across clause anchors, titles, and prose of a spec (`core` / `js-api` / `web-api`). Ranked anchor-exact > title > anchor > prose, with snippets for body matches.

Parameters* required

limitinteger

Max hits.

query*string

Search text.

specstring

Which spec (default core).one of core · js-api · web-api

proposal_listList WebAssembly proposals + phases. Filter by `status` (phase-0…phase-5, finished, inactive), `phase` (0–5), `champion`, `affects` (core|js-api|web-api), or `contains`.5 params

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`.

Parameters* required

affectsstring

Affected spec (finished only).

championstring

Champion substring.

containsstring

Name/champion substring.

phaseinteger

Numeric phase 0–5.

statusstring

Lifecycle status.one of phase-0 · phase-1 · phase-2 · phase-3 · phase-4 · phase-5

Readme

wasm-mcp

Model Context Protocol server for the WebAssembly core specification. SHA-pinned, read-only, deterministic — safe to host as a public unauthenticated endpoint.

Not affiliated with, endorsed by, or sponsored by the W3C WebAssembly Community Group or Working Group.

What it gives you

View the full README on GitHub

Details

Repository: github.com/xyzzylabs/wasm-mcp
Website: mcp.xyzzylabs.ai/wasm
Category: Search & Web Crawling
Package: wasm-mcp
Transport: STDIO, HTTP
Registry: MCP registry, active
Tools verified: Nov 6, 2026

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wasm-mcp

Install

Tools

Readme

wasm-mcp

What it gives you

Details

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