wasm-mcp

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wasm-mcpStructured MCP for the WebAssembly spec

Instruction, type, section, and proposal lookup over the WebAssembly specification for any MCP-speaking AI agent — SHA-pinned, deterministic, read-only. Run it locally over stdio, or hit the hosted Cloudflare Worker over HTTP.

Tool reference
Get started
GitHub
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Spec lookup for AI agents

Any MCP client (Claude Code, Claude Desktop, Cursor, MCP Inspector) gets instruction_get, type_get, section_get, spec_search, and more — structured JSON answers grounded on real spec text instead of grep'd HTML. Every answer carries a stable anchor and the rendered spec URL.

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9 tools

spec_version · instruction_get / list / search · type_get · section_get / list · spec_search · proposal_list

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The instruction set, structured

497 instructions with binary opcodes, stack type signatures, categories (numeric, vector, reference, control, memory, …), introducing version (1.0 / 2.0 / 3.0), and validation + execution anchors. Look up by mnemonic (i32.add) or opcode (0x6a).

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Sections, types & proposals

972 anchor-addressable spec clauses with cleaned prose and cross-references, a 47-entry type catalog (value types + type forms), and the full WebAssembly/proposals phase list.

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Deterministic over pinned data

All data is fetched and indexed at build time from a pinned commit of WebAssembly/spec and baked into the package. Same input → same output. No network at request time.

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Two ways to run it

Local stdio via `npx wasm-mcp`, or the hosted Cloudflare Worker over streamable HTTP. Same MCP protocol, same tools, two transports.

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Safe to host

Read-only, no execution (never compiles, validates-by-running, or instantiates any Wasm), no auth, no secrets, no PII. The hosted endpoint is anonymous and IP-rate-limited.

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Auto-refreshing

A scheduled workflow SHA-diffs the upstream repos daily and ships a patch release when the spec moves — npm package and hosted Worker stay current automatically.

Unofficial / community project — not affiliated with, endorsed by, or maintained by the W3C WebAssembly Community Group or Working Group. It reads the publicly published WebAssembly specification.

Install + run ​

json
// Wire into Claude Code via .mcp.json:
{
  "mcpServers": {
    "wasm": { "command": "npx", "args": ["wasm-mcp"] }
  }
}
sh
# Streamable-HTTP MCP endpoint — no install:
https://wasm-mcp.chicoxyzzy.workers.dev/mcp

See Get started for a 5-minute walkthrough, or the Tool reference for every tool's inputs and examples.

Released under the MIT License.

wasm-mcp v0.1.0 · © 2026 xyzzy_labs