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 an embedding model (e.g., qwen3-embedding:0.6b)

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

Setup

1. Ensure spec is present (only external requirement):

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

   Note: storage/ (pre-built vectors), engine262/lib/, and graphology/ are included in the package.

2. Build knowledge graph (first time only, if using custom spec):

   bun run build
   

MCP Configuration

Add to your MCP client configuration:

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "ask262": {
      "command": "bun",
      "args": ["run", "/path/to/ask262/src/mcp-server.ts"]
    }
  }
}

OpenCode (.opencode/mcp.json):

{
  "servers": {
    "ask262": {
      "command": "bun",
      "args": ["run", "src/mcp-server.ts"]
    }
  }
}

Via global install (after bun install -g ask262):

{
  "mcpServers": {
    "ask262": {
      "command": "ask262"
    }
  }
}

Via bunx (no installation required):

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

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

License

ISC