You can generate types for the plug tools by using the cli. 
npx mcplug types <PLUG_ID>
This will generate a <PLUG_NAME>.d.ts file in the src or root directory of your project. You can then use the type in your code by passing it as generic of the mcplug function. 
const tools = await mcplug<MCPLUG_YOUR_PLUG_NAME>({
  token: PLUG_TOKEN,
  id: PLUG_ID
});

const result = await generateText({
  model: openai("gpt-4o"),
  messages: [
    {
      role: "user",
      content: "What is the weather in Paris?"
    }
  ],
  // Necessary to let the LLM use the tools in a loop if needed and generate a response
  maxSteps: 10,
  tools
});
After that, the toolCalls or toolResults properties of the result will be typed and you will be able to use them safely in your code.

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Specifying the folder

You can specify the folder of the generated types by using the --folder flag. 
npx mcplug types <PLUG_ID> --output src/types