Ask262

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

Features

• Vector search ECMAScript specification sections using semantic queries
• Execute JavaScript in engine262 and capture which spec sections are hit
• Knowledge graph mapping spec sections to implementation functions
• 1-second timeout on code execution for safety

Prerequisites

• Bun: Version 1.0.0 or higher (install)
• Ollama: Installed locally with qwen3-embedding:0.6b model pulled (ollama pull qwen3-embedding:0.6b)

Environment Variables

Ask262 uses Bun's built-in .env support (no dotenv package needed).

Setup:

# Copy the example file
cp .env.example .env

# Edit with your values
nano .env  # or use your preferred editor

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:

# Use Fireworks for embeddings (faster, cloud-based)
ASK262_EMBEDDING_PROVIDER=fireworks
FIREWORKS_API_KEY=fw_your_key_here

# Or use local Ollama (default)
# ASK262_EMBEDDING_PROVIDER=ollama
# OLLAMA_HOST=http://localhost:11434

Installation

# Install globally with bun
bun install -g ask262

# Or run directly without installing
bunx ask262

# Or clone and install
git clone https://github.com/bendtherules/ask262
cd ask262
bun install

MCP Configuration

Add to your MCP client configuration using bunx (no installation required):

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "ask262": {
      "command": "bunx",
      "args": ["ask262"]
    }
  }
}

OpenCode (global config ~/.config/opencode/opencode.json or project config opencode.json):

stdio (local process):

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "ask262": {
      "type": "local",
      "command": ["bunx", "ask262"],
      "enabled": true
    }
  }
}

http (stateless JSON server):

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "ask262": {
      "type": "remote",
      "url": "http://localhost:8081/mcp",
      "enabled": true
    }
  }
}

Start the HTTP server first:

bun run ask262-http     # Development
ask262-http             # After npm install -g
# Or with custom port:
ASK262_PORT=8080 ask262-http

Available Tools

Tool	Description
ask262_search_spec_sections	Vector search ECMAScript spec for relevant sections
ask262_get_section_content	Retrieve full content from a spec section
ask262_evaluate_in_engine262	Execute JS in engine262 and capture spec section marks

Testing

# Run MCP server tests
bun run test-mcp-server

# Test evaluate tool with timeout
bun run test-evaluate-timeout

# Test search functionality
bun run test-search-spec-sections

Development

For development or using a custom ECMAScript specification:

1. Clone and setup:

   git clone https://github.com/bendtherules/ask262
   cd ask262
   bun install
   

2. Ensure spec is present:

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

3. Build knowledge graph (if using custom spec):

   bun run build
   

4. Release to npm (maintainers only):

   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