The Tdweb NPM package does have type definitions, but those type definitions do not cover the JSON API.

Here you can use type definitions for JSON API of Tdweb. There is a prebuilt type definition, an example file to show how to use it, and a generator so you can generate it from your own td_api.tl

Note: Your PC needs to be powerful enough to process 600KB of type definitions for every word you type.

To generate a TypeScript type definitions file from your own td_api.tl file:

1. Install Node.js if you don't have it

2. Clone this repository and run npm install

3. Replace td_api.tl in the folder with your version

4. [Optional] Copy the contents of the table in https://core.telegram.org/tdlib/options and save it in options.txt (rows separated by line breaks, cells separated by tabs). Doing this will add TDLib options types to generated types.

5. Run npm start

   Note: By default, the generator includes some differences between Tdweb API and JSON API. To disable this behavior, use the following command: npm start -- --disable-tdweb-additional-types