Chapter 16: Building Packs in Other Languages

Worka v2 supports multiple language SDKs. Each SDK provides:

• A typed MCP tool interface
• A2UI builders
• In‑process transport inside the WASM runtime

This means you do not run external HTTP servers. Tools are invoked directly by the host inside the pack sandbox.

If you choose a non‑Rust SDK, use the same structure as the Rust pack:

my-pack/
├── aip.json
├── src/
└── assets/ locales/ sql/

Each SDK provides its own build tooling to compile to WASM. Refer to the SDK documentation for your language of choice. const toolArgs = params.arguments;

// ... (we will add routing logic next) });

### Step 4: Implementing and Routing Tools

It\'s good practice to define your tool logic in separate functions and then use a map or a `switch` statement to call the correct one.

Let\'s implement our `greet` tool and a simple router.

```javascript
// Define the logic for the greet tool
const greet = (params) => {
  if (!params || !params.name) {
    // It\'s good practice to validate your parameters
    throw new Error('Missing \'name\' parameter');
  }
  return { greeting: `Hello, ${params.name}!` };
};

// Create a map to hold all your tool handlers
const toolHandlers = {
  greet: greet,
  // another_tool: anotherToolFunction,
};

// Inside your app.post('/', ...) handler:
const handler = toolHandlers[toolName];

if (handler) {
  try {
    const result = handler(toolArgs);
    // Send a successful response
    res.json({ jsonrpc: '2.0', result });
  } catch (e) {
    // Send an error response if the tool logic throws an error
    res.status(400).json({ 
      jsonrpc: '2.0', 
      error: { code: -32602, message: e.message }
    });
  }
} else {
  // Handle the case where the tool name doesn't exist
  res.status(404).json({ 
    jsonrpc: '2.0', 
    error: { code: -32601, message: 'Tool not found' }
  });
}

This structure makes it easy to add new tools. Simply write a new function and add it to the toolHandlers object. The worka dev process will automatically restart your Node.js server when you save your changes, giving you the same hot-reloading experience as with Rust servers.