Ask262

io.github.bendtherulesPublished by GitHub account bendtherulesv0.0.13Updated Oct 24, 2026

MCP server for understanding Javascript internals from ECMAScript specification.

VerifiedStreamable HTTPWeb executableKnowledge & MemoryDeveloper Tools

Overview

AI-generated overview

Ask262 lets an assistant search the ECMAScript specification, read spec sections, and run JavaScript in engine262 to see which spec parts execute.

What you can do
Search the ECMAScript specification by semantic query and retrieve the full content of matching sections. Execute JavaScript in engine262 and capture the spec sections that run, with marking of important code parts. Use a knowledge graph that maps spec sections to implementation functions. Code execution is capped by a one-second timeout.
When to use it
Useful when you need to understand JavaScript language internals, trace behavior back to ECMAScript spec text, or check how a snippet behaves in a spec-faithful engine.
Requirements
A remote endpoint is available with no local setup; the README also documents a local install needing Bun 1.0.0 or higher and Ollama with the qwen3-embedding:8b model, or a Fireworks cloud embedding option configured through FIREWORKS_API_KEY.
Before you install
The evaluate tool runs JavaScript on the server, though execution is limited to a one-second timeout. The optional Fireworks embedding provider requires an API key supplied through FIREWORKS_API_KEY. The chat interface mentioned in the README requires registering an account.

Installation

In SourceWeft

  1. Open Ask262 in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/io.github.bendtherules%2Fask262/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "ask262": {
      "type": "http",
      "url": "https://ask262.mcp.bendtherules.io/mcp"
    }
  }
}

README

Ask262

MCP server for exploring the ECMAScript specification and its implementation in engine262.

🎮 Try it now

The fastest way to tinker with JavaScript internals:

  • Ask262 Chat — Ask questions in natural language (register new account)
  • MCP Inspector — Direct access to all mcp tools, no signup needed
  • npx add-mcp "https://ask262.bendtherules.in/mcp"

Features

  • Vector search ECMAScript specification sections using semantic queries
  • Execute JavaScript in engine262 and capture spec sections, with ask262Debug.startImportant() to mark the key parts of your code
  • Knowledge graph mapping spec sections to implementation functions
  • 1-second timeout on code execution for safety

Available Tools

ToolDescription
ask262_search_spec_sectionsVector search ECMAScript spec for relevant sections
ask262_get_section_contentRetrieve full content from a spec section
ask262_evaluate_in_engine262Execute JS and capture spec sections, with "important" marking to focus on relevant parts

Quick Start (Hosted Instance)

Use the hosted MCP server without any local setup:

Preferred Method: npx add-mcp

Install ask262 MCP server to your client with one command:

bash
npx add-mcp "https://ask262.bendtherules.in/mcp"

Manual Configuration

If you prefer to configure manually:

Claude Desktop (claude_desktop_config.json):

json
{  "mcpServers": {    "ask262": {      "url": "https://ask262.bendtherules.in/mcp"    }  }}

OpenCode (~/.config/opencode/opencode.json):

json
{  "$schema": "https://opencode.ai/config.json",  "mcp": {    "ask262": {      "type": "remote",      "url": "https://ask262.bendtherules.in/mcp",      "enabled": true    }  }}

Local Installation

Prerequisites

  • Bun: Version 1.0.0 or higher (install)
  • Ollama: Installed with qwen3-embedding:8b
    (ollama pull qwen3-embedding:8b)

Setup

bash
# Clone and installgit clone https://github.com/bendtherules/ask262cd ask262bun install
# Or install globallybun install -g ask262

Environment Configuration

Copy .env.example and configure:

bash
cp .env.example .env

Key variables:

  • ASK262_EMBEDDING_PROVIDER: Choose ollama (local) or fireworks (cloud). Default: ollama
  • OLLAMA_HOST: Ollama server URL. Default: http://localhost:11434
  • FIREWORKS_API_KEY: Required if using Fireworks. Get from https://app.fireworks.ai
  • ASK262_PORT: HTTP server port. Default: 8081

Example .env:

bash
# Use Fireworks for embeddings (faster, cloud-based)ASK262_EMBEDDING_PROVIDER=fireworksFIREWORKS_API_KEY=fw_your_key_here
# Or use local Ollama (default)# ASK262_EMBEDDING_PROVIDER=ollama# OLLAMA_HOST=http://localhost:11434

Local MCP Configuration

Claude Desktop (claude_desktop_config.json):

stdio (no server needed)
json
{  "mcpServers": {    "ask262": {      "command": "bunx",      "args": ["ask262"]    }  }}
http (requires server)
json
{  "mcpServers": {    "ask262": {      "url": "http://localhost:8081/mcp"    }  }}

⬇️ Required for HTTP config above:

bash
bun run ask262-http # start HTTP server

OpenCode (~/.config/opencode/opencode.json):

stdio (no server needed)
json
{  "$schema": "https://opencode.ai/config.json",  "mcp": {    "ask262": {      "type": "local",      "command": ["bunx", "ask262"],      "enabled": true    }  }}
http (requires server)
json
{  "$schema": "https://opencode.ai/config.json",  "mcp": {    "ask262": {      "type": "remote",      "url": "http://localhost:8081/mcp",      "enabled": true    }  }}

⬇️ Required for HTTP config above:

bash
bun run ask262-http # start HTTP server

HTTP Server Endpoints:

EndpointDescription
GET /healthHealth check
GET/POST /mcpMCP protocol endpoint
GET /MCP Inspector UI (auto-connects to /mcp)

Note: /mcp is defined before the inspector's catch-all / route to ensure proper request handling.

Testing

bash
# Run MCP server testsbun run test-mcp-server
# Test evaluate tool with timeoutbun run test-evaluate-timeout
# Test search functionalitybun run test-search-spec-sections

Development

For development or using a custom ECMAScript specification:

  1. Clone and setup:

    bash
    git clone https://github.com/bendtherules/ask262cd ask262bun install

  2. Ensure spec is present:

    • ./spec-built/multipage/ - Built ECMAScript spec HTML files

    Steps -

    1. git clone https://github.com/tc39/ecma262
    2. npm i && npm run build
    3. copy out/ from ecma262 to spec-built/ in this repo

  3. Build vectors (lancedb)

    bash
    bun run ingest

  4. Release to npm (maintainers only):

    bash
    bun run release

    This will:

    • Check for uncommitted git changes
    • Bump patch version (e.g., 0.0.1 → 0.0.2)
    • Fix any hard links in storage/
    • Run checks and release

    Other options: bun run release -- --minor, bun run release -- --major, or bun run release -- --no-bump

License

ISC

Source: Readme.md at commit 1715462

Tools

0
SourceWeft has not read this server's tools yet.

Version history

1
  1. v0.0.13LatestSep 16, 2026

Score

40% of the applicable checks met

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  • Reached in the last 30 daysRequired25 pts

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  • Auth declaredRequired10 pts

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  • Tools listed15 pts

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  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts

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