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 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 core 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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Core + JS-API + Web-API

section_get, section_list, and spec_search span all three specs in the WebAssembly/spec repo via a `spec` argument — the core language, the JavaScript embedding API (WebAssembly.instantiate, Module, Memory, …), and the Web-platform integration (streaming compilation).

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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.

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 ​

The stdio launch command is the same for every MCP client; only the config file's location differs (check your client's MCP docs).

json
{
  "mcpServers": {
    "wasm": { "command": "npx", "args": ["wasm-mcp"] }
  }
}
sh
# Streamable-HTTP MCP endpoint — no install:
https://mcp.xyzzylabs.ai/wasm/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 v0.2.16 · © 2026 xyzzy_labs